Physics Book - User contributions [en]

Semiconductor Devices

2020-11-15T23:19:27Z

Msharm:

Last edited by Megha Sharma (Fall 2020)

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

[[File:IMG 2424.jpg|Diagram of an EK diagram|350 px|]]

===Detecting Doping===

Secondary ion mass spectroscopy (SIMS) is a very powerful technique for the analysis of impurities in solids. SIMS can be utilized for semiconductor dopant profiling. The technique relies on removal of material from a solid by sputtering and on analysis of the sputtered ionized species; all elements are detected. SIMS can detect dopant densities as low as 10^14 cm^-3. The dopant density profile that is generated is based on the ion signal versus time plot. The time axis is converted to a depth axis by measuring the depth of the crater at the end of the measurement assuming a constant sputtering rate. For example, boron is implanted into silicon at a given energy and dose to create a standard. The secondary ion signal is calibrated by assuming the total amount of boron in the sample to equal to the implanted boron. The unknown sample of B implanted into silicon is then compared to the standard. However, there is limited dynamic range of the SIMS instrument that can contribute to slightly deeper junctions and discrepancies in the lowly doped portions of the profile. When sputtering from a highly doped region to a lowly doped region, the crater walls still contain the entire doping density profile. SIMS also measures total dopant density, regardless of activation. Thus going back to the silicon-boron example, the dopant profile shows dependence of electrical activation of boron implanted into silicon on implant dose and activation temperature.

[[File:Sims-technique-schematic.png|frame|none|left|Example of SIMS]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

===A Computational Model===

[https://phet.colorado.edu/sims/cheerpj/semiconductor/latest/semiconductor.html?simulation=semiconductor Semiconductor Simulation]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

Another example that was discussed previously on this page is the usage of silicon in photovoltaic devices. Silicon is used because it is the first semiconductor that was commercialized successfully. Many commercial companies are very proficient in making silicon devices, so the silicon is not necessarily used because it is the best material for harnessing the electricity from the photovoltaic effect. The silicon crystals allow the power to reach the external electrical circuit, but the silicon doesn't absorb sunlight as efficiently because it needs to be ten to one hundred times thicker than an advanced thin-film cell. It is also favored because of the low maintenance. A unique oxide forms when silicon is exposed to high temperatures that serves to neutralize defects on the silicon surface. The frontier for replacing the silicon looks quite bleak because of the practicality of manufacturing silicon crystalline semiconductors, but new research is being conducted on using silicon with lower purity or combining it with other semiconductor materials.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

Introduction to Secondary Ion Mass Spectrometry (SIMS) technique. (n.d.). Retrieved November 15, 2020, from https://www.cameca.com/products/sims/technique

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T23:15:58Z

Msharm:

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

[[File:IMG 2424.jpg|Diagram of an EK diagram|350 px|]]

===Detecting Doping===

Secondary ion mass spectroscopy (SIMS) is a very powerful technique for the analysis of impurities in solids. SIMS can be utilized for semiconductor dopant profiling. The technique relies on removal of material from a solid by sputtering and on analysis of the sputtered ionized species; all elements are detected. SIMS can detect dopant densities as low as 10^14 cm^-3. The dopant density profile that is generated is based on the ion signal versus time plot. The time axis is converted to a depth axis by measuring the depth of the crater at the end of the measurement assuming a constant sputtering rate. For example, boron is implanted into silicon at a given energy and dose to create a standard. The secondary ion signal is calibrated by assuming the total amount of boron in the sample to equal to the implanted boron. The unknown sample of B implanted into silicon is then compared to the standard. However, there is limited dynamic range of the SIMS instrument that can contribute to slightly deeper junctions and discrepancies in the lowly doped portions of the profile. When sputtering from a highly doped region to a lowly doped region, the crater walls still contain the entire doping density profile. SIMS also measures total dopant density, regardless of activation. Thus going back to the silicon-boron example, the dopant profile shows dependence of electrical activation of boron implanted into silicon on implant dose and activation temperature.

[[File:Sims-technique-schematic.png|frame|none|left|Example of SIMS]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

===A Computational Model===

[https://phet.colorado.edu/sims/cheerpj/semiconductor/latest/semiconductor.html?simulation=semiconductor Semiconductor Simulation]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

Another example that was discussed previously on this page is the usage of silicon in photovoltaic devices. Silicon is used because it is the first semiconductor that was commercialized successfully. Many commercial companies are very proficient in making silicon devices, so the silicon is not necessarily used because it is the best material for harnessing the electricity from the photovoltaic effect. The silicon crystals allow the power to reach the external electrical circuit, but the silicon doesn't absorb sunlight as efficiently because it needs to be ten to one hundred times thicker than an advanced thin-film cell. It is also favored because of the low maintenance. A unique oxide forms when silicon is exposed to high temperatures that serves to neutralize defects on the silicon surface. The frontier for replacing the silicon looks quite bleak because of the practicality of manufacturing silicon crystalline semiconductors, but new research is being conducted on using silicon with lower purity or combining it with other semiconductor materials.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

Introduction to Secondary Ion Mass Spectrometry (SIMS) technique. (n.d.). Retrieved November 15, 2020, from https://www.cameca.com/products/sims/technique

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T22:54:17Z

Msharm: /* References */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

[[File:IMG 2424.jpg|Diagram of an EK diagram|350 px|]]

===Detecting Doping===

Secondary ion mass spectroscopy (SIMS) is a very powerful technique for the analysis of impurities in solids. SIMS can be utilized for semiconductor dopant profiling. The technique relies on removal of material from a solid by sputtering and on analysis of the sputtered ionized species; all elements are detected. SIMS can detect dopant densities as low as 10^14 cm^-3. The dopant density profile that is generated is based on the ion signal versus time plot. The time axis is converted to a depth axis by measuring the depth of the crater at the end of the measurement assuming a constant sputtering rate. For example, boron is implanted into silicon at a given energy and dose to create a standard. The secondary ion signal is calibrated by assuming the total amount of boron in the sample to equal to the implanted boron. The unknown sample of B implanted into silicon is then compared to the standard. However, there is limited dynamic range of the SIMS instrument that can contribute to slightly deeper junctions and discrepancies in the lowly doped portions of the profile. When sputtering from a highly doped region to a lowly doped region, the crater walls still contain the entire doping density profile. SIMS also measures total dopant density, regardless of activation. Thus going back to the silicon-boron example, the dopant profile shows dependence of electrical activation of boron implanted into silicon on implant dose and activation temperature.

[[File:Sims-technique-schematic.png|frame|none|left|Example of SIMS]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

Another example that was discussed previously on this page is the usage of silicon in photovoltaic devices. Silicon is used because it is the first semiconductor that was commercialized successfully. Many commercial companies are very proficient in making silicon devices, so the silicon is not necessarily used because it is the best material for harnessing the electricity from the photovoltaic effect. The silicon crystals allow the power to reach the external electrical circuit, but the silicon doesn't absorb sunlight as efficiently because it needs to be ten to one hundred times thicker than an advanced thin-film cell. It is also favored because of the low maintenance. A unique oxide forms when silicon is exposed to high temperatures that serves to neutralize defects on the silicon surface. The frontier for replacing the silicon looks quite bleak because of the practicality of manufacturing silicon crystalline semiconductors, but new research is being conducted on using silicon with lower purity or combining it with other semiconductor materials.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

Introduction to Secondary Ion Mass Spectrometry (SIMS) technique. (n.d.). Retrieved November 15, 2020, from https://www.cameca.com/products/sims/technique

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T22:48:23Z

Msharm: /* Semiconductors & Applications in Solid-State Physics */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

[[File:IMG 2424.jpg|Diagram of an EK diagram|350 px|]]

===Detecting Doping===

Secondary ion mass spectroscopy (SIMS) is a very powerful technique for the analysis of impurities in solids. SIMS can be utilized for semiconductor dopant profiling. The technique relies on removal of material from a solid by sputtering and on analysis of the sputtered ionized species; all elements are detected. SIMS can detect dopant densities as low as 10^14 cm^-3. The dopant density profile that is generated is based on the ion signal versus time plot. The time axis is converted to a depth axis by measuring the depth of the crater at the end of the measurement assuming a constant sputtering rate. For example, boron is implanted into silicon at a given energy and dose to create a standard. The secondary ion signal is calibrated by assuming the total amount of boron in the sample to equal to the implanted boron. The unknown sample of B implanted into silicon is then compared to the standard. However, there is limited dynamic range of the SIMS instrument that can contribute to slightly deeper junctions and discrepancies in the lowly doped portions of the profile. When sputtering from a highly doped region to a lowly doped region, the crater walls still contain the entire doping density profile. SIMS also measures total dopant density, regardless of activation. Thus going back to the silicon-boron example, the dopant profile shows dependence of electrical activation of boron implanted into silicon on implant dose and activation temperature.

[[File:Sims-technique-schematic.png|frame|none|left|Example of SIMS]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

Another example that was discussed previously on this page is the usage of silicon in photovoltaic devices. Silicon is used because it is the first semiconductor that was commercialized successfully. Many commercial companies are very proficient in making silicon devices, so the silicon is not necessarily used because it is the best material for harnessing the electricity from the photovoltaic effect. The silicon crystals allow the power to reach the external electrical circuit, but the silicon doesn't absorb sunlight as efficiently because it needs to be ten to one hundred times thicker than an advanced thin-film cell. It is also favored because of the low maintenance. A unique oxide forms when silicon is exposed to high temperatures that serves to neutralize defects on the silicon surface. The frontier for replacing the silicon looks quite bleak because of the practicality of manufacturing silicon crystalline semiconductors, but new research is being conducted on using silicon with lower purity or combining it with other semiconductor materials.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T22:47:02Z

Msharm: /* Semiconductors & Applications in Solid-State Physics */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

[[File:IMG 2424.jpg|frame|none|left|Diagram of an EK diagram]]

===Detecting Doping===

Secondary ion mass spectroscopy (SIMS) is a very powerful technique for the analysis of impurities in solids. SIMS can be utilized for semiconductor dopant profiling. The technique relies on removal of material from a solid by sputtering and on analysis of the sputtered ionized species; all elements are detected. SIMS can detect dopant densities as low as 10^14 cm^-3. The dopant density profile that is generated is based on the ion signal versus time plot. The time axis is converted to a depth axis by measuring the depth of the crater at the end of the measurement assuming a constant sputtering rate. For example, boron is implanted into silicon at a given energy and dose to create a standard. The secondary ion signal is calibrated by assuming the total amount of boron in the sample to equal to the implanted boron. The unknown sample of B implanted into silicon is then compared to the standard. However, there is limited dynamic range of the SIMS instrument that can contribute to slightly deeper junctions and discrepancies in the lowly doped portions of the profile. When sputtering from a highly doped region to a lowly doped region, the crater walls still contain the entire doping density profile. SIMS also measures total dopant density, regardless of activation. Thus going back to the silicon-boron example, the dopant profile shows dependence of electrical activation of boron implanted into silicon on implant dose and activation temperature.

[[File:Sims-technique-schematic.png|frame|none|left|Example of SIMS]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

Another example that was discussed previously on this page is the usage of silicon in photovoltaic devices. Silicon is used because it is the first semiconductor that was commercialized successfully. Many commercial companies are very proficient in making silicon devices, so the silicon is not necessarily used because it is the best material for harnessing the electricity from the photovoltaic effect. The silicon crystals allow the power to reach the external electrical circuit, but the silicon doesn't absorb sunlight as efficiently because it needs to be ten to one hundred times thicker than an advanced thin-film cell. It is also favored because of the low maintenance. A unique oxide forms when silicon is exposed to high temperatures that serves to neutralize defects on the silicon surface. The frontier for replacing the silicon looks quite bleak because of the practicality of manufacturing silicon crystalline semiconductors, but new research is being conducted on using silicon with lower purity or combining it with other semiconductor materials.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T22:45:33Z

Msharm: /* The Main Idea */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

Example of an EK Diagram:
[[File:IMG 2424.jpg|Diagram of an EK diagram|350 px|]]

===Detecting Doping===

Secondary ion mass spectroscopy (SIMS) is a very powerful technique for the analysis of impurities in solids. SIMS can be utilized for semiconductor dopant profiling. The technique relies on removal of material from a solid by sputtering and on analysis of the sputtered ionized species; all elements are detected. SIMS can detect dopant densities as low as 10^14 cm^-3. The dopant density profile that is generated is based on the ion signal versus time plot. The time axis is converted to a depth axis by measuring the depth of the crater at the end of the measurement assuming a constant sputtering rate. For example, boron is implanted into silicon at a given energy and dose to create a standard. The secondary ion signal is calibrated by assuming the total amount of boron in the sample to equal to the implanted boron. The unknown sample of B implanted into silicon is then compared to the standard. However, there is limited dynamic range of the SIMS instrument that can contribute to slightly deeper junctions and discrepancies in the lowly doped portions of the profile. When sputtering from a highly doped region to a lowly doped region, the crater walls still contain the entire doping density profile. SIMS also measures total dopant density, regardless of activation. Thus going back to the silicon-boron example, the dopant profile shows dependence of electrical activation of boron implanted into silicon on implant dose and activation temperature.

[[File:Sims-technique-schematic.png|frame|none|left|Example of SIMS]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

Another example that was discussed previously on this page is the usage of silicon in photovoltaic devices. Silicon is used because it is the first semiconductor that was commercialized successfully. Many commercial companies are very proficient in making silicon devices, so the silicon is not necessarily used because it is the best material for harnessing the electricity from the photovoltaic effect. The silicon crystals allow the power to reach the external electrical circuit, but the silicon doesn't absorb sunlight as efficiently because it needs to be ten to one hundred times thicker than an advanced thin-film cell. It is also favored because of the low maintenance. A unique oxide forms when silicon is exposed to high temperatures that serves to neutralize defects on the silicon surface. The frontier for replacing the silicon looks quite bleak because of the practicality of manufacturing silicon crystalline semiconductors, but new research is being conducted on using silicon with lower purity or combining it with other semiconductor materials.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

File:Sims-technique-schematic.png

2020-11-15T22:43:58Z

Msharm:

Semiconductor Devices

2020-11-15T22:40:59Z

Msharm: /* Connectedness */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

Example of an EK Diagram:
[[File:IMG 2424.jpg|Diagram of an EK diagram|350 px|]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

Another example that was discussed previously on this page is the usage of silicon in photovoltaic devices. Silicon is used because it is the first semiconductor that was commercialized successfully. Many commercial companies are very proficient in making silicon devices, so the silicon is not necessarily used because it is the best material for harnessing the electricity from the photovoltaic effect. The silicon crystals allow the power to reach the external electrical circuit, but the silicon doesn't absorb sunlight as efficiently because it needs to be ten to one hundred times thicker than an advanced thin-film cell. It is also favored because of the low maintenance. A unique oxide forms when silicon is exposed to high temperatures that serves to neutralize defects on the silicon surface. The frontier for replacing the silicon looks quite bleak because of the practicality of manufacturing silicon crystalline semiconductors, but new research is being conducted on using silicon with lower purity or combining it with other semiconductor materials.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T22:37:23Z

Msharm: /* Semiconductors & Applications in Solid-State Physics */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

Example of an EK Diagram:
[[File:IMG 2424.jpg|Diagram of an EK diagram|350 px|]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T22:31:11Z

Msharm: /* Semiconductors & Applications in Solid-State Physics */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram (shown below). It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

Example of an EK Diagram:
[[File:IMG 2424.jpg]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T22:29:01Z

Msharm: /* Semiconductors & Applications in Solid-State Physics */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram. It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

[[File:EK.jpg]]

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

File:IMG 2424.jpg

2020-11-15T22:27:41Z

Msharm: Diagram of an EK diagram

Diagram of an EK diagram

Semiconductor Devices

2020-11-15T22:17:27Z

Msharm:

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material, a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===Semiconductors & Applications in Solid-State Physics===

The key principle that is often used in solid-state physics is the carrier effective mass. This refers to the mass a particle (within the semiconductor) seems to have when interacting with other identical particles in a thermal distribution. This constant is simplified version of the band theory and influences measurable properties of a solid, including the efficiency of the devices that semiconductors are used in for example, solar cell efficiency and integrated circuit speed. So, how do we actually measure the carrier effective masses in a semiconductor?

Large parts of the simplicity of the free electron gas model can be saved by assigning effective masses to the carriers. Only electrons and holes at the band edges (characterized by a wave vector kex) participate in the generation - recombination process that is the hallmark of semiconductors. A particle's effective mass is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution. One of the results from the band theory of solids is that the movement of particles over long distances can be very different from their motion in a vacuum. The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. Sometimes the effective mass can be considered to be a simple constant of a material, however, the value of effective mass depends on the purpose for which it is used, and can vary depending on a number of factors. For electrons or electron holes in a solid, the effective mass is usually stated in units of the rest mass of an electron, me (9.11×10−31 kg). In these units it is usually in the range 0.01 to 10, but can also be lower or higher—for example, reaching 1,000 in exotic heavy fermion materials, or anywhere from zero to infinity (depending on definition) in graphene. The effective mass of a semiconductor is obtained by fitting the actual electron diagram around the conduction band minimum or the valence band maximum by a parabola - this is called an E-K diagram. It shows the relationship between the energy and momentum of available quantum mechanical states for electrons in the material. As it simplifies the more general band theory, the electronic effective mass can be seen as an important basic parameter that influences measurable properties of a solid, including everything from the efficiency of a solar cell to the speed of an integrated circuit.

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T21:54:26Z

Msharm: /* Semiconductor Devices */

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===What are Semiconductors?===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. They have a good conductivity between conductors (these tend to be metals) and nonconductors (these insulators tend to be ceramics). Semiconductors do not have to originate organically - the most common semiconductor material are pure elements such as silicon and germanium, but impurities are often added to control the conductivity levels. This process is called doping.

Due to low cost, reliability, ability to control conductivity, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material,a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Semiconductor Devices

2020-11-15T18:44:09Z

Msharm:

Last edited by Megha Sharma (Fall 2020)
Last Edited by Joey Buehler (Fall 2018)

Allison Youngsman 12/2/15

'''Claimed by Michael Eden (Fall 2016)'''

'''edited by Eric Lee (Fall 2016)'''

===Semiconductor Devices===

Semiconductor devices are electronic components with the electronic properties of semiconductors. Silicon, germanium, gallium arsenide, organic semiconductors are among the most common semiconductors used in these devices. Semiconductors are materials that are neither good conductors or good insulators. Due to low cost, reliability, and compactness, semiconductors are used for a wide range of applications. They also have a wide range of current and voltage handling capabilities, contributing to their suitability for a number of operations. They are commonly found in power devices, optical sensors, and light emitters. Perhaps more importantly, they are readily integrated into microelectronic uses as key elements for the majority of electronic systems, including communications, consumer, data-processing, and industrial-control equipment.

[[File:Intelthing.jpg|frame|border|right|A raw board with many transistors in it!]]
[[File:transistor.png|frame|none|left|An fully built integrated circuit.]]

==The Main Idea==

Semiconductors work by using the electric properties of the p-n junction that makes up a diode. The junction is formed through a process called doping. Doping involves turning silicon into a conductor by changing the behavior of its electrons. In n-type doping, a phosphorus/arsenic impurity is introduced so that the valence will have free electrons to allow a electric current to flow. Since extra electrons are negative in charge, this type of doping is called n-type doping referred to by "n" in the p-n junction. In the p-type doping, a boron/gallium impurity is introduced to the silicon lattice so the valence will have an empty electron orbital. Because the empty area implies the absence of an electron and thus creates a positive charge, "p" was assigned as the name of the doping type.

[[File:n-type.gif|frame|border|right|N-Type Material]]

[[File:p-type.png|frame|none|left|P-Type Material]]

The two most useful forms of semiconductor devices are diodes and transistors. Diodes are the simplest semiconductor device, which conducts current easily in one direction but conducts almost no current in the other direction. These are made by joining two pieces of semiconducting material,a junction called a "p-n" junction. One of the pieces contains a small amount of boron and the other contains a small amount of phosphorus. Transistors are constructed through two semiconducting junctions, or "p-n" junctions. These are the most common elements in digital circuits. The conductivity of these semiconductors can be controlled by introduction of an electric or magnetic field, by exposure to light or heat, or by mechanical deformation of a doped monocrystalline grid. Due to this, semiconductors are extremely useful and can be altered to fit specific purposes.

===A Mathematical Model===

Semiconductors operate based on the concept of thermal energy exciting electrons and causing them to jump to the next higher (unoccupied) energy band.
These electrons can pick up energy (and drift speed) from an applied electric field. The filled energy band is called the “valence” band, and the nearly unoccupied higher energy band is called the “conduction” band. The number of electrons excited into the conduction band is proportional to a value called the Boltzmann constant, equivalent to the value:
<math>
e^{-E_{\text{gap}} / k_B T}
</math>.
Therefore, high conductivity (corrosponding to a favorable Boltzmann factor) can be calculated according to
<math>
T = 2 \pi \sqrt{\frac{m}{k}}
</math>,
where <math>m</math> is the mass of the object in kilograms, <math>k</math> is the spring constant, and <math>T</math> is the period of oscillation in seconds. In addition, the total conventional current in a semiconductor can be calculated, according to the equation
<math>
I = e n_n A u_n E + e n_p A u_p E
</math>.

===A Conceptual Model===
The following diagram demonstrates how electron excitement in semiconductors works. Semiconductors are materials with small band gaps between the valence band and conduction bands. As you can see, a small amount of thermal energy is needed to promote an electron to the conduction band in a semiconductor.

[[File:conceptual.png|frame|none|left|A Conceptual Model of the Semiconductor]]

==History==
'''1874'''
Ferdinand Braun discovers that current flows freely in only one direction when a metal point and a galena crystal are put together.

'''1901'''
Jagadis Bose takes ownership of the discovery of the semiconductor crystal for detecting radio waves.

'''1940'''
Russell Ohl discovers the p-n junction.

'''1940s'''
Semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. They were most commonly used as detectors in radios, through devices called "cat's whiskers". During the era of WWII, researchers worked with semiconductors and cat's whiskers to make more effective diodes.

'''1947'''
William Shockley and John Bardeen worked together to create a triode-like semiconductor: the first transistor. They realized that if there were some way to control the flow of the electrons from the emitter to the collector of this newly discovered diode, an amplifier could be built.The first transistor was officially created on the 23rd of December, 1947.

'''1956'''
John Bardeen, William Shockley, and another researcher named Walter Houser Brattain were credited for the invention and awarded a Nobel Prize for physics in 1956 for their work. After this, the utilization of semiconductors soon advanced to even more complicated applications.

'''1960s'''
In the late 1960s, transistors moved from being germanium based to silicon based. Gordon K Teal was most responsible for this advancement, and his company, Texas Instruments, profited greatly. Portable radios are just one popular invention that benefited from silicon based semiconductors. Now, silicon based semiconductors constitute more than 95 percent of all semiconductor hardware sold worldwide.

'''1970s'''
Silicon technology is modernized and the race to fit all semiconductor processor technology into one chip is most active.

'''2000'''
Nobel Prize in physics awarded to Zhores I. Alferov and Herbert Kroemer for developing semiconductor heterostructures used in high-speed- and opto-electronics and half to Jack S. Kilby "for his part in the invention of the integrated circuit."

[[File:transistorwork.png|frame|none|none|John Bardeen, William Shockley, and Walter Houser Brattain, winners of the Nobel Prize for their invention of the transistor, are pictured above.]]

===Connectedness===

Semiconductors are crucial to modern technology, and are used for memory storage as well as so many other technological innovations. This technology is used every day by millions of people for thousands of different applications. Most people in the world have used semiconductors in one way or another, even if they weren't aware of it. It is specifically connected to the major of Biomedical Engineering through memory storage and the complex computer programs used every day to conduct business and create simulations for the furthering of biomedical research. All industrial applications of semiconductors are very applicable, from amplifiers to transistors to silicon disks. Without semiconductors, much of the technology that the general population relies on today would not be possible.

Semiconductors are used in essentially every part of this technological and electronically-dependent world we live in today. They have both conductor and insulator properties and includes all of the metal we see in wires. Computers, phones, and other electronic devices all use semiconductors to fulfill their functions such as communication and efficiency. The most important aspect of semiconductors is utilization, which is shown through the use of switches. Inside electronic devices, the switches exist in extremely large numbers, which is why electronic devices process information in an incredible speed with surprising efficiency.

Semiconductors are connected to chemical engineering largely through their industrial creation. The process of depositing each layer of material onto the wafer is a chemical process controlled by deposition of gaseous metals onto the wafer. There are an incredible variety of steps from material preparation to packaging which can be optimized by an eager chemical engineer.

==Types of Semiconductors==

===Diodes===

[[File:Diode_current_wiki.png|314px|thumb|right|top|IV Characteristic of a Diode]]

Diodes are really great! In a simple sense, they can give you a "point of no return" in your circuit (but they can actually do much more than that).
Three interesting things should be observed from the IV characteristic shown to the right:

# For small positive voltages and above, the diode does not limit the current (the line is almost vertical)!
# For small to larger negative voltages, the diode resists current (the line is almost flat).
# For a large negative voltage (the breakdown voltage) the diode gives up (no one is perfect).

We can formally define this line with the Shockley Diode Equation, which formalizes this observation:

<math display="block">
I = I_S \left( e^{\frac{V_D}{n V_T}} - 1 \right)
</math> where

<math>I</math> is the diode current,

<math>I_S</math> is the reverse bias saturation current (or scale current),

<math>V_D</math> is the voltage across the diode,

<math>V_T</math> is the thermal voltage, and

<math>n</math> is the ideality factor, (1 if the diode is ideal, greater than 1 if it is imperfect).

A great practical use for diodes is a rectifier:

[[File:Gratz.rectifier.en.svg|frame|border|center|Diodes groups the positive and negative signals together]]

This makes sure that when a positive voltage appears on either line, it is redirected to a single positive line, and the same for the negatives.
BAM! AC to DC, that's pretty easy, you can charge your phone with that.
In reality a capacitor is added in parallel with the load to try to smooth out the ripples.
A voltage regulator after the rectifying step is also a popular choice, depending on the needs of the application.

Another super useful application is that of a back up power supply: simply connect two supplies in parallel with the positive terminals buffered with diodes. The higher of the two voltages is always used and the transition between supplies is seamless.

===Zener Diodes===

Some diodes (Zener) are made to have small breakdown voltages.
Since during breakdown the IV curve is almost vertical (it's really an exponential), the current is independent (almost) from voltage.
You can then wire up a Zener diode in reverse to a point in the circuit, and it will accept as much current as it needs to to reach that
breakdown voltage. Because of this a great practical use for Zener diodes is a voltage regulator since the voltage is set when the diode is
manufactured and does not change greatly with a varying power supply.

===Bipolar Junction Transistors===

[[Image:BJT NPN symbol (case).svg|75px|thumb|NPN BJT]]
[[Image:BJT PNP symbol (case).svg|75px|thumb|PNP BJT]]

Shortly after the invention of the first transistor (which was OK), the BJT landed, which was the first transistor to be prolific in the field.
It was made using two alternating NP junctions as shown below:

[[File:NPN BJT (Planar) Cross-section.svg|frame|border|center|NPN BJT (Planar) Cross-section]]

Really transistors (and by extension all that is needed for a computer to be built) are amplifiers (OK, to build all computers you need an inverting amplifier, but one can be built using the BJT).
If one is used to thinking of them as an electrically-controlled switch, you can simply think of a switch as an amplifier with a gain of <math>\infty</math>.

A simple model of a BJT is a linear current-controlled current source, i.e. the base to emitter (B to E) current <math>I_{BE}</math> is proportional to
the collector to emitter (C to E) current <math>I_{CE}</math>. The proportionality constant <math>\beta</math> can be thought of as the "gain" of the
transistor. This gives a relationship of <math>I_{CE} = \beta I_{BE}</math>.

[[File:Current-Voltage relationship of BJT.png|thumb|right|Current-Voltage relationship of BJT]]

Sadly there is no source of infinite power, so the output to our amplifier tops off when it can't supply any more power.
This can be seen with the graph on the right.
The simple model then only works for the tiny linear part at the start of the graph, even so its not ''that'' linear.
The BJT proved to be power hungry, pretty non-linear and sensitive to the environment (temperature, etc.).
These growing pains lead to a new development, called the MOSFET.

===MOSFETs===

MOSFETs are the coolest, they are less power-hungy and easier to work with when compared to BJTs.
Instead of having a current control, which uses power and gets the control and the output signal coupled together,
a MOSFET's output is controlled by the electric Field (the F in MOSFET) the control signal creates on one of the plates of the MOSFET.
Since the control signal and the output are electrically disconnected (as you would see in a capacitor) there is much less power draw
from this type of transistor.

We can see how linear this thing is with its IV characteristic: <math>I_D= \mu_n C_{ox}\frac{W}{L} \left( (V_{GS}-V_{th})V_{DS}-\frac{V_{DS}^2}{2} \right)</math>

Apart from the control signal <math>V_{DS}</math> and constants, the voltage across the output portion of the MOSFET is linearly related to the current!
This means that the MOSFET behaves like a voltage controlled resistor, and a resistor is something much easier to analyse and work with.

Most circuits with an enormous amount of transistors these days use primarily MOSFETs. BJTs are still useful for temperature and light sensing
applications.

==Industrial Semiconductor Fabrication==

Semiconductors are mass produced in specialized factories called foundries or fabs. The process consists of multiple chemical and photolithographic steps which add layers to a wafer usually made of silicon. The entire process usually takes around 2 months but it can last up to 4.

The semiconductor product is rated by the size of the chip's process gate length, where processes with smaller gate lengths are typically harder to make. There are 10-20 different sized chips being fabricated around the world as of 2018. There is an immense amount of attention and money being dedicated to improving semiconductor fabrication process efficiency.

[[File:feol.png|frame|none|left|Steps to fabricate a semiconductor device]]

==Examples==

===Simple===
[[File:Cat'swhiskerdetector.jpg]]

A simple application of a semiconductor would be the Cat's Whisker detector for radios, invented in the early 1900s.

===Moderate===
[[File:Opticallsensor.jpg]]

Optical sensors are moderately difficult applications of semiconductors. Optical sensors are electronic detectors that convert light into an electronic signal. They are used in many industrial and consumer applications. An example would include lamps that turn on automatically in response to darkness.

===Difficult===

[[File:Complicated_semiconductor.jpg]]

A very complicated application of a semiconductor is its use in modern cellular phone devices, such as its use here in the iPhone 6.

== See also ==

Related Wiki pages:

-Transformers

-Resistors and conductivity

-Superconductors

-Electric Fields

-Transformers from a physics standpoint

===Further reading===

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

===External links===

Wikipedia page about semiconductors:

https://en.wikipedia.org/wiki/Semiconductor_device

Encyclopedia entry about semiconductors, including the history of semiconductors:

http://www.britannica.com/technology/semiconductor-device

Information about Diodes:

https://en.wikipedia.org/wiki/Diode

Information about BJTs:

https://en.wikipedia.org/wiki/Bipolar_junction_transistor

Information about MOSFETs:

https://en.wikipedia.org/wiki/MOSFET

Semiconductor Device Fabrication

https://en.wikipedia.org/wiki/Semiconductor_device_fabrication

==References==
Brain, Marshall. "How Semiconductors Work." HowStuffWorks. N.p., 25 Apr. 2001. Web. 27 Nov. 2016.

Chabay, Sherwood. (n.d.). Matter and Interactions (4th ed., Vol. 2). Raleigh, North Carolina: Wiley.

Electronics and Semiconductor. (n.d.). Retrieved December 3, 2015, from http://www.plm.automation.siemens.com/en_us/electronics-semiconductor/devices/

Huculak, M. (2014, September 19). IPhone 6 and iPhone 6 Plus get teardown by iFixit • The Windows Site for Enthusiasts - Pureinfotech. Retrieved December 3, 2015, from http://pureinfotech.com/2014/09/19/iphone-6-iphone-6-plus-get-teardown-ifixit/

John Bardeen, William Shockley and Walter Brattain at Bell Labs, 1948. (n.d.). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/John_Bardeen#/media/File:Bardeen_Shockley_Brattain_1948.JPG

The Nobel Prize in Physics 1956. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/1956/summary/>

The Nobel Prize in Physics 2000. NobelPrize.org. Nobel Media AB 2018. Sun. 25 Nov 2018. <https://www.nobelprize.org/prizes/physics/2000/summary/>

เซ็นเซอร์แสง (Optical Sensor) - Elec-Za.com. (2014, July 28). Retrieved December 3, 2015, from http://www.elec-za.com/เซ็นเซอร์แสง-optical-sensor/

Semiconductor device. (2015, November 30). Retrieved December 3, 2015, from https://en.wikipedia.org/wiki/Semiconductor_device

Semiconductor Fabrication. (25 November 2018). http://www.iue.tuwien.ac.at/phd/rovitto/node10.html

Shah, A. (2013, May 13). Intel loses ground as world's top semiconductor company, survey says. Retrieved December 3, 2015, from http://www.pcworld.com/article/2038645/intel-loses-ground-as-worlds-top-semiconductor-company-survey-says.html

Shaw, R. (2014, November 1). The cat's-whisker detector. Retrieved December 3, 2015, from http://rileyjshaw.com/blog/the-cat's-whisker-detector/

Sze, S. (2015, October 1). Semiconductor device | electronics. Retrieved December 3, 2015, from http://www.britannica.com/technology/semiconductor-device

Sze, S. (1981). Physics of semiconductor devices (2nd ed.). New York: Wiley.

"Timeline." Timeline | The Silicon Engine | Computer History Museum. The Silicon Engine, n.d. Web. 27 Nov. 2016.

[[Category:Simple Circuits]]

Vectors

2019-11-23T22:46:13Z

Msharm:

== Megha Sharma ==

This page defines and describes vectors.

==The Main Idea==

In mathematics and physics, a vector is a quantity with both a magnitude and a direction in space. The magnitude of a vector is a scalar value which can represent a variety of characteristics, depending on the situation. The magnitude of the vector (and the vector itself) has units corresponding to the characteristic it represents. The direction refers to the angle from the positive x -axis. Thus, the magnitude refers to the length and the direction refers to the angle. Note that a vector does not necessarily extend from one point in real, physical space to another; unless the magnitude is in units of length, the magnitude of the vector usually represents a property that exists at a single point in real, physical space, or at no position in particular.

===A Mathematical Model===

====Simple Examples of Vector Quantities====

To understand what it means for a vector to have both a magnitude and a direction, and to understand why the magnitude and direction together are often considered a single quantity, it can be helpful to consider an example. The [[Velocity]] of an object is an example of a vector quantity. The speed of the object, often given in meters per second (m/s), is a scalar value describing how quickly the object is moving. Speed is the magnitude of the velocity vector. However, the object's movement happens in a particular spatial direction, which the speed alone does not tell us. The direction of the object's movement is also a part of the velocity vector. Together, speed and direction comprise the velocity vector and give a complete description of an object's motion at a point in time. Another example of a vector is position; the distance of a point from the origin of a coordinate system can be represented as the magnitude of a vector, and this distance together with a direction describes exactly where a point can be found.

====Unit Vectors====

A unit vector is a vector whose magnitude is 1 by design.

Some unit vectors are normalized regular vectors. For example, <math>\hat{r}</math> is the normalized version of some vector <math>\vec{r}</math>. Normalization is the process of setting a vector's magnitude to 1. This is done to discard information about the vector's magnitude while retaining information about its direction. To normalize a vector, the following formula can be used: <math>\hat{a} = \frac{\vec{a}}{|\vec{a}|}</math>

Certain letters represent specific unit vectors. For example, <math>\hat{i}</math>, <math>\hat{j}</math>, and <math>\hat{k}</math> (alternatively, <math>\hat{x}</math>, <math>\hat{y}</math>, and <math>\hat{z}</math>) are unit vectors pointing in the +x, +y, and +z directions respectively. Non-Cartesian coordinate systems often have their own unit vectors; for example, 2D polar coordinates make use of the <math>\hat{r}</math> and <math>\hat{\theta}</math> unit vectors.

====Notation====

Surrounding a vector by | symbols denotes its magnitude: <math>|\vec{b}|</math>.

A variable representing a vector is typically written as a letter with an arrow over it: <math>\vec{a}</math>. The arrow may one-sided to make it easier to write. Alternatively, a vector variable might simply be written as a boldface letter: a. Which letter is used depends on the context; for example, <math>\vec{v}</math> represents velocity.

A specific component of a vector (see the section titled "forms") is denoted by a subscript: cx. For example, qy represents the y component of some vector <math>\vec{q}</math>.

A unit vector is denoted by a letter with a ^ symbol (called a "hat") written over it: <math>\hat{d}</math> (read as "d-hat").

====Visually Representing Vectors====

Vectors are visually represented by arrows. The length of the arrow represents the magnitude of the vector, while the direction the arrow points in represents the direction of the vector. If a vector exists at a particular point in space, the "tail" of the arrow (the end without the V shape) should be placed at that point.

This example shows a visual representation of the velocity vector of a ball, which is moving to the right at a speed of 5m/s.

[[File:Vectorvisualrepresentation.png]]

====Forms====

The information necessary to describe a specific vector can be presented in several forms.

Magnitude and direction form

In this form, the magnitude and the direction of the vector are explicitly stated. The statement describing direction might be a cardinal direction (ex. "north"), a direction on a graph (ex. "the +x direction"), or an angle (ex. "210<math>^\circ</math> from the x axis counterclockwise"), depending on the situation. Magnitude and direction form is often used in word problems because it is easy for humans to understand.

Component form

In this form, the vector is divided into components, each representing a different coordinate direction. In 2D space, these are the x and y directions. In 3D space, these are the x, y, and z directions. Each component tells how much the vector extends in that particular direction. Often, the three components are written enclosed by angle brackets and separated by commas. For example, the vector <2,0,-3> describes a vector that extends 2 units in the +x direction, 0 units in the y direction, and 3 units in the -z direction. Most vector operations described below can only be performed if the vectors are in component form, so this form may be necessary to do math for certain problems. Furthermore, programming languages store vectors in component form.

Unit vector form

In this form, the vector is expressed as a sum of unit vectors, each corresponding to a different coordinate direction. The symbols <math>\hat{i}</math>, <math>\hat{j}</math>, and <math>\hat{k}</math> OR the symbols <math>\hat{x}</math>, <math>\hat{y}</math>, and <math>\hat{z}</math> are used to represent unit vectors in the x, y, and z directions respectively. Consider the vector <2,0,-3>. It can be expressed in unit vector form as <math>2\hat{i} - 3\hat{k}</math>, meaning 2 times the x direction unit vector minus 3 times the z direction unit vector (see vector operations). While often considered its own form, unit vector form is very similar to component form, as the information describing the vector is stored in the same values. All references to component form in the rest of this page also apply to unit vector form.

[[File:Vectorsdifferentforms.png]]

Note that regardless of which form is used, an n-dimensional vector requires n values to mathematically describe. For example, consider a 3-dimensional vector. Describing this vector in component form requires an x value, a y value, and a z value. Describing it in magnitude and direction form requires one value to give the magnitude of the vector and two to give the its direction (the direction of a 3D vector could be described using, say, its polar angle <math>\theta</math> and its azimuthal angle <math>\phi</math>). A 1-dimensional vector (such as the velocity of a particle whose movement is constrained to the x axis) can be described using only 1 value whose sign indicates the vector's direction.

Converting between forms

It is possible to convert vectors from one form to another using simple trigonometry.

To find the magnitude of a vector in component form, use the Pythagorean theorem: add the squares of the components and take the square root of the result. For a 2D vector, <math>|\vec{a}| = \sqrt{a_x^2 + a_y^2}</math>.

To find the direction of a vector in component form, use inverse trigonometric functions. For a 2D vector, <math>\theta = \tan^{-1}(\frac{a_y}{a_x})</math>, where <math>\theta</math> is the angle vector <math>\vec{a}</math> makes with the x axis in the counterclockwise direction.

To find the components of a vector in magnitude and direction form, use trigonometric functions. For a 2D vector, <math>a_x = |\vec{a}|\cos\theta</math> and <math>a_y = |\vec{a}|\sin\theta</math>, where <math>\theta</math> is the angle vector <math>\vec{a}</math> makes with the x axis in the counterclockwise direction.

====Vector Operations====

It is possible to perform a variety of mathematical operations on vectors, both with other vectors and with scalars. These operations appear in a variety of formulas in physics. To make the operations easier to learn, they are defined below assuming all vectors to be 3-dimensional; the more general n-dimensional definitions look more confusing. If necessary, it is easy to guess how to perform each operation with n-dimensional vectors by extrapolating from the 3-dimensional case.

Addition:

<math>\vec{a} + \vec{b} = (a_x + b_x)\hat{i} + (a_y + b_y)\hat{j} + (a_z + b_z)\hat{k}</math>.

In other words, to add two vectors, simply add their like components to form the new components. The new vector is called the "resultant" of the other two. Visually, if the tail of one vector is placed at the tip of another, their resultant will extend from the tail of the second vector to the tip of the first:

[[File:Vectoraddition.png|600px]]

Subtraction:

<math>\vec{a} - \vec{b} = (a_x - b_x)\hat{i} + (a_y - b_y)\hat{j} + (a_z - b_z)\hat{k}</math>.

In other words, to subtract two vectors, simply subtract their like components to form the new components.

Multiplication by scalar:

<math>k \vec{a} = ka_x\hat{i} + ka_y\hat{j} + ka_z\hat{k}</math>.

In other words, multiplying a vector by a scalar multiplies each of that vector's components by that scalar. Multiplying a vector by a scalar multiplies its magnitude by that scalar and does not affect its direction, unless the scalar is negative, in which case the direction of the vector is reversed.

[[File:Vectorscalarmultiplication.png|400px]]

Division by scalar:

<math>\frac{\vec{a}}{k} = \frac{a_x}{k}\hat{i} + \frac{a_y}{k}\hat{j} + \frac{a_z}{k}\hat{k}</math>.

In other words, dividing a vector by a scalar divides each of that vector's components by that scalar. Dividing a vector by a scalar divides its magnitude by that scalar and does not affect its direction, unless the scalar is negative, in which case the direction of the vector is reversed.

Dot product (also called scalar product):

<math>\vec{a}\cdot\vec{b} = a_xb_x + a_yb_y + a_zb_z</math>.

In other words, the dot product of two vectors is the sum of the products of their like components. Note that this is a scalar value.

It is important to note that the dot product of two vectors has a specific value: <math>\vec{a}\cdot\vec{b} = |\vec{a}||\vec{b}|\cos\theta</math>, where <math>\theta</math> is the angle between the vectors.

Cross product (also called vector product):

<math>\vec{a}\times\vec{b} = (a_yb_z - a_zb_y)\hat{i} + (a_zb_x - a_xb_z)\hat{j} + (a_xb_y - a_yb_x)\hat{k}</math>.

This is equivalent to the following matrix determinant, which may be easier to remember:

<math>\begin{vmatrix}
\hat{i} & \hat{j} & \hat{k} \\
a_x & a_y & a_z \\
b_x & b_y & b_z
\end{vmatrix}</math>

Note that this is a vector quantity. It is important to note that the magnitude of the cross product of two vectors has a specific value: <math>|\vec{a}\times\vec{b}| = |\vec{a}||\vec{b}|\sin\theta</math>, where <math>\theta</math> is the angle between the vectors. The direction of the cross product of two vectors is perpendicular to the plane in which those vectors lie and is given by the [[Right Hand Rule]]. 2D vectors do not have cross products. While the other operations listed here are commutative, associative (where the associative property is defined), and distributive over addition; cross product multiplication is not associative and is anticommutative (<math>\vec{a}\times\vec{b} = -\vec{b}\times\vec{a}</math>), meaning that if the order of the factors is reversed, their cross product will be reversed in direction.

Transformations

A variety of transformations are defined for vectors, including multiplication by matrices and projection onto spaces. These transformations use a combination of the six basic operations above to manipulate vectors in more complex ways. These transformations lie outside of the scope of this page and this course due to their complexity and irrelevance to introductory physics.

===A Computational Model===

In VPython, vector objects are in component form; each one has an x, y, and z component. Recall that in VPython, using the default camera orientation, the +x axis points to the right, the +y axis points upwards, and the +z axis points out of the plane of the screen towards the viewer. The constructor for a vector object is the word "vec" or "vector," and it takes three arguments, which define its x, y and z components respectively. A line to create a vector called "velocity" might look like this:

velocity = vec(3,-1,2)

To access or modify a specific component of a vector object, its name should be followed by a period and an x, y, or z. For example, to change the x component of the above velocity vector from 3 to 5, the following line might be used:

velocity.x = 5

In VPython, vectors have many uses. The position of each object is defined as a vector; the position vector's tail lies at the origin and its head lies at the center of the object in question. Furthermore, the dimensions of a rectangular prism (a "box" object) are defined as a vector; the x component determines its width, the y component its height, and the z component its thickness.

To graphically represent a vector such as an electric field, "arrow" objects should be used. In addition to taking a position vector (which determines the position of the arrow's tail), arrow objects take an "axis" vector, which determines their size and shape. To represent a vector, simply make it the axis of an arrow object.

==Examples==

===Simple===

Vector <math>\vec{a}</math> is <2,4,2>. Vector <math>\vec{b}</math> is <-1,1,3>. What is the magnitude of the vector <math>\vec{a} - 2\vec{b}</math>?

Solution:

<math>\vec{a} - 2\vec{b} = <2,4,2> - 2 * <-1,1,3> </math>

<math> = <2,4,2> - <-2,2,6> </math>

<math> = <4,2,-4></math>

We are asked to find the magnitude of this vector, so let us use the Pythagorean theorem with its components:

<math>|<4,2,-4>| = \sqrt{4^2 + 2^2 + (-4)^2}</math>

<math> = \sqrt{16 + 4 + 16} </math>

<math> = \sqrt{36} </math>

<math> = 6 </math>

===Intermediate===

An airplane is travelling in still air at 240m/s in the direction 35<math>^\circ</math> south of west. A wind begins to blow; the wind has a speed of 80m/s in the direction 15<math>^\circ</math> east of north. What should be the new velocity of the plane relative to the air around it to maintain its original trajectory? You may give your answer in component form (+x is east, +y is north).

[[File:Vectorsplaneproblem.png]]

Solution:

The vector sum of the new velocity of the plane <math>\vec{v_{p,1}}</math> and the velocity of the wind <math>\vec{v_w}</math> should equal the original velocity of the plane <math>\vec{v_{p,0}}</math> (see [[Relative Velocity]]):

[[File:Vectorsplanesolution.png]]

<math> \vec{v_{p,1}} + \vec{v_w} = \vec{v_{p,0}} </math>

<math> \vec{v_{p,1}} = \vec{v_{p,0}} - \vec{v_w} </math>

Let us convert the given vectors to component form for easier subtraction. The +x and +y directions will be east and north respectively.

<math>\vec{v_{p,0}} = <240\cos(215^\circ), 240\sin(215^\circ)></math>m/s (35<math>^\circ</math> south of west is 215<math>^\circ</math> above the x axis)

<math>\vec{v_{p,0}} = <-196.6, -137.7> </math>m/s

<math>\vec{v_w} = <80\cos(75^\circ), 80\sin(75^\circ)></math>m/s (15<math>^\circ</math> east of north is 75<math>^\circ</math> above the x axis)

<math>\vec{v_w} = <20.7, 77.3> </math>m/s

Now let us subtract:

<math> \vec{v_{p,1}} = \vec{v_{p,0}} - \vec{v_w} </math>

<math> \vec{v_{p,1}} = <-196.6, -137.7> - <20.7, 77.3> </math>m/s

<math> \vec{v_{p,1}} = <-217.3, -214.9> </math>m/s

===Difficult===

What is the angle between the vectors <2,5,-2> and <3,-4,-1>?

Solution:

The dot product between two vectors is equal to the product of their magnitudes times the cosine of the angle between them. Let us use this property to find the angle between the given vectors.

<math> <2,5,-2> \cdot <3,-4,-1> = |<2,5,-2>| * |<3,-4,-1>| * \cos\theta </math>

Rearranging this yields

<math> \theta = \cos^{-1}\frac{<2,5,-2> \cdot <3,-4,-1>}{|<2,5,-2>| * |<3,-4,-1>|} </math>

Let us evaluate the dot product and simplify:

<math> \theta = \cos^{-1}\frac{2(3) + 5(-4) + (-2)(-1)}{\sqrt{2^2 + 5^2 + (-2)^2} * \sqrt{3^2 + (-4)^2 + (-1)^2}} </math>

<math> \theta = \cos^{-1}\frac{-12}{\sqrt{33 * 26}} </math>

<math> \theta = 114^\circ </math>

==Connectedness==

Vectors are used in many fields and levels of physics. Kinematics, for example, studies the relationships between the position vector and its time derivatives (velocity, acceleration). Force is also a vector quantity, as are certain system properties such as linear and angular momentum. Vector fields are commonly used in electricity and magnetism, as well as in fluid dynamics.

==History==

It is unknown who first developed the idea of vectors, but the oldest known reference to vectors is in the work Mechanics by Hero of Alexandria (first century AD), which described their addition. At this point, however, the idea of a vector was little more than a line segment with a specific orientation; they had a length extending from one point in physical space to another but were not used to represent anything else.

In the early 19th century, several mathematicians and physicists (including Caspar Wessel (1745-1818), Jean Robert Argand (1768-1822), Carl Friedrich Gauss (1777-1855)), and William Rowan Hamilton (1805-1865) used 2D vectors to represent complex numbers; one component would represent the real value and another would represent the imaginary value. Hamilton would also become the first to use the word "vector." August Ferdinand Möbius (1790-1868) contributed to vector math in his 1827 book The Barycentric Calculus, in which he developed the convention of labeling vectors with letters and defined the multiplication of a vector by a scalar. Hermann Grassmann (1809-1877) wrote in his 1844 book Ausdehnungslehre (German for "The Calculus of Extension") that vectors could exist in space of any number of dimensions and described much of what would become linear algebra, which makes ample use of vectors.

The modern language and conventions surrounding vectors come largely from notes created by J. Willard Gibbs (1839--1903), a professor at Yale University.

==See also==

===External links===
Mathematical Computations on Vectors: [http://ocw.mit.edu/courses/mathematics/18-02sc-multivariable-calculus-fall-2010/1.-vectors-and-matrices/part-a-vectors-determinants-and-planes/session-1-vectors/MIT18_02SC_notes_0.pdf [http://ocw.mit.edu/courses/mathematics/18-02sc-multivariable-calculus-fall-2010/1.-vectors-and-matrices/part-a-vectors-determinants-and-planes/session-1-vectors/MIT18_02SC_notes_0.pdf]

Computational Work with Vectors: [http://vpython.org/contents/docs/vector.html http://vpython.org/contents/docs/vector.html]

Basics of Vectors: [https://www.physics.uoguelph.ca/tutorials/vectors/vectors.html https://www.physics.uoguelph.ca/tutorials/vectors/vectors.html]

===Further Reading===

Vector Analysis by Josiah Willard Gibbs

Introduction to Matrices and Vectors by Jacob T. Schwartz

==References==
[https://www.mathsisfun.com/algebra/vectors.html https://www.mathsisfun.com/algebra/vectors.html]

[http://ocw.mit.edu/courses/mathematics/18-02sc-multivariable-calculus-fall-2010/1.-vectors-and-matrices/part-a-vectors-determinants-and-planes/session-1-vectors/MIT18_02SC_notes_0.pdf http://ocw.mit.edu/courses/mathematics/18-02sc-multivariable-calculus-fall-2010/1.-vectors-and-matrices/part-a-vectors-determinants-and-planes/session-1-vectors/MIT18_02SC_notes_0.pdf ]

[http://mathinsight.org/vector_introduction http://mathinsight.org/vector_introduction]

[http://www.math.mcgill.ca/labute/courses/133f03/VectorHistory.html http://www.math.mcgill.ca/labute/courses/133f03/VectorHistory.html]

[[Category: Geometry]]