What is Semiconductor physics: Definition and 39 Discussions

A semiconductor material has an electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities ("doping") into the crystal structure. When two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions and electron holes, at these junctions is the basis of diodes, transistors and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.
Semiconductor devices can display a range of useful properties, such as passing current more easily in one direction than the other, showing variable resistance, and sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion.
The conductivity of silicon is increased by adding a small amount (of the order of 1 in 108) of pentavalent (antimony, phosphorus, or arsenic) or trivalent (boron, gallium, indium) atoms. This process is known as doping and the resulting semiconductors are known as doped or extrinsic semiconductors. Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature. This is contrary to the behavior of a metal in which conductivity decreases with an increase in temperature.
The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of charge carriers in a crystal lattice. Doping greatly increases the number of charge carriers within the crystal. When a doped semiconductor contains free holes it is called "p-type", and when it contains free electrons it is known as "n-type". The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants. A single semiconductor device crystal can have many p- and n-type regions; the p–n junctions between these regions are responsible for the useful electronic behavior. Using a hot-point probe, one can determine quickly whether a semiconductor sample is p- or n-type.Some of the properties of semiconductor materials were observed throughout the mid 19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector, a primitive semiconductor diode used in early radio receivers. Developments in quantum physics led in turn to the invention of the transistor in 1947, the integrated circuit in 1958, and the MOSFET (metal–oxide–semiconductor field-effect transistor) in 1959.

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  1. Roger Dalton

    Dependence of Hall coefficient on temperature in semiconductors

    My first assumption is that the temperature dependence on the mobilities can be neglected, and so we would have: $$R_H(T)= \frac{1}{e} \frac{p_v(T)\mu_h^2-n_c(T)\mu_e^2}{(p_v(T)\mu_h+n_c(T)\mu_e)^2}$$ The expression for the electron and hole densities could be derived from...
  2. rogdal

    A Empirical tight-binding sp3s* band structure of semiconductors

    I'm simulating on code the tight-binding sp3s* bandstructure of certain semiconductors, such as GaAs, AlP, InP, ZnSe, etc. with spin-orbit coupling at a temperature of T = 0 K but I'm having trouble at finding the corresponding spin-orbit splitting parameters. For example, I've found in this...
  3. cemtu

    Solid State Good Condensed Matter Physics Books and Semiconductor Physics Books

    Can you please recommend me some condensed matter physics study books and semi-conductor physics study books? Much Appreciated!
  4. lelouch_v1

    Donor and Acceptor Concentrations in a Si speciment

    At the left side we have the n-side of the junction, whereas at the right we have the p-side. I am a little confused over $N_D$ and $N_A$ at the n-side. Do the Ga atoms interact with the As ones, so we have $N_D = 2*10^{16} \text{cm}^{-3}$, or not, ans thus we have $N_A=2*10^{16} \text{cm}^{-3}$...
  5. orochi

    Learning about condensed matter physics as a particle physicist

    I am on my first year of my master's degree in nuclear and particle physics, and right now i am ending my first semester, where i decided to take a course in physics of semiconductors. As i end this semester i start to wonder if there was any use in learning about this subject, as it seems like...
  6. R

    Does Drain Current Increase if Doping Increases?

    I'm an EE with only a surface knowledge of solid state. I know this forum is mostly for students but I don't know where else to find a lot of physicists. Also, please forgive me if this is a dumb question. For a circuit I want to build, I need a transistor that can conduct > 10,000 A, but does...
  7. Mr_Allod

    Calculating the speed of a JFET

    Hello there, I believe here I need to find the capacitance of the junction between the P-doped gate and N-channel. Then I could find the RC time constant although I am not sure if there's something more I need to find the speed of the JFET? What I'm unsure of is the depletion width h to use...
  8. Mr_Allod

    Built in Voltage of 3-Layer PN Junction

    For a normal PN junction I would try to find $V_{bi}$ by integrating the carrier density (eg. the electrons n) from one region to the other: $$\int_{n_{p0}}^{n} \frac {dn}{n} = \frac {q}{kT}\int_{V_p}^{V_n} dV$$ Which would yield: $$V_{bi}=V_n-V_p=\frac...
  9. A

    Silicon and Germanium semiconductor mixtures used in component manufacturing?

    Can Silicon and Germanium semiconductors mixture (chemical reaction) with some other chemical elements (if required) assist in creating new and existing robust electronic components? Si + Ge + ? + ? = Can this assist in quantum computing?
  10. cemtu

    What makes up a "current" in solid state physics?

    If there is some incoming light that has hit electrons of a N-type doped silicon and broke loose these electrons from their covalent bounds and excited them to the conduction band and also excited the electrons in the donor energy level to the conduction band as well, here we know that, the...
  11. cemtu

    I Exploring Ionised Atoms, Free Electrons & Energy Levels

    Homework Statement:: Ionised atom, free electron, conduction band, donor energy level and acceptor energy level Relevant Equations:: None I have some confusion about the concept of some electronic bands and energy levels. Beyond valance band, in a solid crystal lattice, For an atom, can...
  12. quixote

    Courses Course on Semiconductor Physics as part of my EE degree

    Hey, need a bit of a help. me, an electrical engg. student is confused at this point that my university offers a course(half semester) on "Electronic Devices(ED)" as they call it; as you can infer from the attachment. As I watch the lectures it turns out to be an intermediate course on the...
  13. M

    Semiconductor Physics: Definition & Relation to Material Sci

    how you can define the term "Semiconductor Physics" and what is the relation between semiconductor Physics and Material Science?
  14. M

    I What subfields does semiconductor physics comprise?

    What subfields semiconductor physics comprise?
  15. C

    Semiconductor physics: Voltage below forward voltage

    Assume we have a diode closed circuit.We connect the p type region of the diode to the positive terminal of the battery(cathode).We connect the n type region of the diode to the negative terminal of the battery(anode).The voltage of the battery is 0.3V .The diode%s intristic se miconductor is...
  16. M

    A 2D Harmonica Oscillator For Holes In Magnetic Field

    Hello I am bemused by a sign convention for Holes, My questions are as follow: For an electron inside the 2D Circular Quantum Well. We can write our Hamiltonian as H = 1/2m * ( p - q A)^2 + 1/2 m w^2 r^2 (Should we use minus in the momentum term? I think for Holes, it is) If we expand this...
  17. Matthew Strasiotto

    Doping semiconductors compounded from various element groups

    Hi all - This is pulled from a past paper - Homework Statement I'm only going to state the components that I find challenging of this problem - The rest will be attached in my solution set. Essentially - given an intrinsic semiconductor comprised of group II-VI elements. Upon doping with group...
  18. D

    Programs Change of Major from Mechanical Engineering to Material Science

    Hello guys, I received an admit to grad school for Mechanical Engineering, where my focus was initially Thermo-Fluids . I've also enquired about the Material Science department at the University(in the USA), and they are willing to let me transfer to the Material Science department provided I...
  19. Dor

    I What should be continuous at the interface of two materials?

    At the interface between: 1) conductor/conductor 2) conductor/semiconductor (or dielectric) 3) semiconductor/semiconductor (or dielectric/dielectric) What quantity should be continuous? Is it the electrochemical potential, only the chemical potential or is it the electric potential? Since they...
  20. Wrichik Basu

    Do carriers move across a p-n junction at 0 K?

    Often a band diagram is used to explain what happens when two pieces of the same semiconductor, one p-doped, one n-doped, are put together. I am a little confused about it, so here is my question. Initially and at ##0\mathrm{K}##, the surplus carriers should be confined to their respective...
  21. A

    I Fluorescence from core shell quantum dots

    What is the reason for enhancement in the intensity of emission due to the introduction of a shell in quantum dots? I do understand the blue shift in quantum dots but how does a shell enhance it?
  22. Wrichik Basu

    B What is the utility of grounding in this Transistor case?

    I am attending an online lecture course on semiconductor physics. While explaining the common emitter mode of transistors, the professor sketched this diagram on the board: (I added something more to explain better) I understand that the emitter has to be at the same potential, and that is...
  23. maverick_starstrider

    I Transport in PV Cells (and pn diodes)

    Hi, I'm having some trouble wrapping my head around some of the concepts and language of charge transport in Photovoltaic cells (and thus pn-diodes). My biggest problem is understanding the role played by the emitter region vs. the depletion region. In a typical PV cell the front emitter...
  24. F

    Semiconductor Physics Books, Online Notes, Websites etc.

    Hi, I am looking for a good book or any other online resource on semiconductor physics. What I need the book to cover is: The PN junction i.e. the diode BJT transistors MOSFETS In particullar I am interested in the derivation of the equations of the above components, the Shockley...
  25. A

    Semiconductor physics: Resistivity,mobility and concentration.

    Homework Statement If a sample of pure silicon at 300 Kelvin has a resistivity of 950Ωm, and if the electron-to-hole mobility ration is 3:1, with the electron mobility equal to 0.12m2V-1s-1, what are the intrinsic hole and electron concentrations? Homework Equations I know resistivity...
  26. H

    Semiconductor Physics: Fraction of Drift Current Flow Due to Electrons

    Homework Statement A certain doped semiconductor at room temperature has the following properties: no = 9 x 1014 / cm3, po = 4 x 1014 / cm3, μe = 800 cm2 / V-s, μh = 400 cm2 / V-s, and (Dh\tauh)1/2 = 10-4 cm. If an electric field is applied, what fraction of the resulting drift current flow...
  27. S

    Semiconductor Physics : Charge carrier concentration change on doping

    Hi, I have a question regarding the change in charge carrier concentration change. For a given semiconductor, say Silicon, when it is not doped, it is easy to understand that {n_0} \times {p_0} = n_i^2, however, on doping with donors to form a n-type semiconductor, we have {n_0} \approx...
  28. R

    Semiconductor Physics - Density of States Calculation Problem?

    Homework Statement Determine the total number of energy states in silicon from the edge of the conduction band to Ec + kT for T = 300K. Homework Equations N = \intg(E)dE The Attempt at a Solution I'm pretty sure I know how to do this one. The only problem is, when I get to the...
  29. P

    Learning Resources - Semiconductor Physics

    Over the past 3 months I've been watching Leonard Susskind's lectures (Stanford) on quantum mechanics and particle physics from YouTube. This has been an enjoyable experience and I would like to further my own education. My interest is in semiconductor physics particularly modelling using the...
  30. W

    Effective mass of Si in semiconductor physics

    Hello, I have the problem, from Sze' book, tunneling current, what is m*? I want to konw the value of it. The m* has many reference, how do I select? My interested device is diode that was doped with Boron and Phosphorus for p-n junction. Thank very much.
  31. L

    Solving Semiconductor Physics: Conduction Electron Density Calculation

    Homework Statement I am asked to show that the conduction electron density in an n type semiconductor is given by: n=\frac{1}{2} \left( -n_0 e^{-(E_c-E_d)/kT} + \sqrt{n_0^2 e^{-2(E_c-E_d)/kT}+4 n_0 N_d e^{-(E_c-E_d)/kT} } \right) where n_0=2(m^* kT/2 \pi \hbar^2 )^{3/2}For low temp p=0 and...
  32. L

    Whats the difference between a vacancy and a hole in semiconductor physics?

    hi, I am reading my notes on semiconductor physics and this is a concept that is puzzling me - i always thought a vacancy and a hole were the same thing. in my notes it says that a hole has the same properties as a full band with one vacancy and so for consistency the hole must have...
  33. D

    Clarification on semiconductor physics in solar cells

    So, I am doing a little bit of research on how energy is created in solar cells. From what I understand, there is just a whole bunch of n and p junctions connected to each other electrons flow the same way. Or, electrons travel one way, and holes travel the other. So when you dope the silicon...
  34. L

    Semiconductor Physics and Devices Textbook

    Hey everyone, I'm wondering if anyone out there could recommend a great intermediate textbook for studying Semiconductor Physics and Semiconductor Devices (PN junctions, BJTs, etc.). Right now I'm using a textbook by Neaman, which is alright but not great. I've asked people the same...
  35. J

    Can anyone suggest a thesis topic on semiconductor physics?

    can anyone suggest a topic on semiconductor physics that is great for a thesis study? thanks
  36. B

    Semiconductor physics (electron-hole lifetimes)

    OK I'm just having a bit of trouble getting my head around this concept. I'm doing a small talk on it as a mini-assignment for solid state, and so I really need to understand this. A semiconductor in thermal equilibrium Now I know that the recombination and generation rates are equal in this...
  37. L

    Programs REU for EE major that wants to get into applied semiconductor physics

    REU for EE major that wants to get into applied semiconductor physics... hello, I am a dual major in EE and compE, with minors in both chemistry and physics (3 credits away from the chem minor, and I would like to take quantum mechanics, contemporary physics, and solid state physics, which will...
  38. R

    Fermi Level & Equilibrium Conditions in Semiconductor Physics

    why is that the fermi level should be constant throught the system under equilibrium conditions? can I know the physical outcome of that condition or the violation of the same?
  39. C

    Question about semiconductor physics

    Hello, my question is the following: we know from books on semiconductor physics that the energy levels of the electrons in a pure semiconductor cristal form in fact bands of energy. I was wondering why these energy levels are in the form of bands an not simple distinct energy levels as...