Semiconductor physics is the branch of solid state physics that focuses on specific properties of semiconductors. It studies dynamics of different perturbations (mainly electrons and holes) in the semiconductor crystal and the ways to affect it.

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Why is an exciton only observed when we excite to the conduction band and not to other electronic level inside the bandgap?

Excitons can be observed when we excite electrons to the conduction band. I don't know about excitons being observed when we excite the electrons to an electronic level that would eventually be in ...
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Why is nitrogen not used as a pentavalent impurity?

I don't understand why nitrogen though a fifth group element is not used as a pentavalent impurity in doping a semiconductor.
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29 views

Polarization selection rules

So, I am just reviewing some of my physics stuff, and I have read something about polarization selection rules in inter-band-transitions in quantum wells. If I calculate them, I get a strength of 1/2 ...
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Is carrier charge density and carrier mobility constant in a given material?

If we assume the semi-conductor is doped by a variable amount, is there some way I can look up carrier charge density for the material in a reference somewhere? What about carrier mobility?
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84 views

Does Saturation velocity in semiconductors have a relation with the wavelength in which the peak in the absorption spectrum occurs?

Saturation velocity is the maximum velocity a charge carrier in a semiconductor, generally an electron, attains in the presence of very high electric fields. (source) I want to know if the ...
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17 views

Can electrons move back into the donor level

In a n-type semiconductor electrons from the donor level move up into the conduction band but can they move back down? Also in a p-type semiconductor electrons move to the acceptor level from the ...
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37 views

How does a minority carrier diffuse?

I have gone through a lot of questions but none of them ask how do the minority carriers approach the depletion layer in the first place. When a p-n junction is formed, negative space charge ...
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32 views

How do we predict electrical properties of a material using scattering data and vice-versa?

I know that the band gap is related to conductivity. What I'm wondering is what it is like for an experimentalist who is trying to figure out what an unknown material, a black box, is doing. The only ...
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N-type semiconductors and the number of holes?

Let us say we have Germanium which has been doped with antimony. Antinomy has a a fifth valence electron not involved in bonding. Is this electron in the valence band? I ask because all texts on the ...
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Please explain The Bias-Dependence Change of Barrier Height of Schottky Diodes under applied Bias

I would like to know how and why does the barrier height of Schottky Diode change under the applied forward and reverse bias conditions.
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229 views

How do the effects of semiconductor doping affect the Hall effect?

For instance, consider number 4 and 5 in the following sample: Using the right hand rule, B points downwards, conventional current points to the right (because of the 5V battery), and therefore, ...
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Effective masses for different direction

Assume we have an indirect semiconductor where the effective mass becomes anisotropic in different directions. Usually, one talks about a mass in parallel and perpendicular direction referring to ...
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Does the Shockley Diode Equation hold in a dynamic circuit?

Consider the following simple photodiode circuit: I've created a real-life version of this circuit, and I've detected that $I$ is oscillating: $$I(t)=I(t+\tau)\tag{$\tau\approx ...
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Donors/Acceptors in Metal Oxides

Can anyone explain to me why most articles describe chromium as an acceptor in titanium dioxide? In TiO2, titanium has the charge state Ti$^{4+}$ and oxygen has the charge state O$^{2-}$. When Cr ...
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Silicon/silicon dioxide interface

Suppose we have an interface of silicon/silicondioxide. If we shine light on the top surface electron-hole pairs are generated in silicon. since there is always a field directing from surface to bulk ...
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How can I simulate a model electronic hole?

Suppose I can solve time-dependent Schrödinger equation for several 1D particles (currently 3). I'd like to see, what an electronic hole is and how it behaves — in a series of numerical experiments. ...
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What is the temperature evolution of the conductance of a quantum chaotic system?

I read this really nice article by Abanin and Levitov: http://arxiv.org/pdf/0704.3608.pdf They argued that the mixing of the quantum edge channel at the vicinity of a PN junction is described by the ...
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65 views

Why can't we dope the intrinsic semiconductors with sixth or second group elements?

Suppose we want to make an n-type silicon semiconductor why do we use arsenic or phosporous as an impurity? Why cant we use selinium or terellium? Infact my doubt is when we use sixth group element ...
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38 views

What factors cause the velocity saturation to occur at different electric fields for different materials?

In semiconductors the velocity of carriers gets saturated after a certain value of electric field. In silicon it occurs at around $10^4 kV/cm$ and in GaAs at some other value. What factors are ...
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15 views

How to obtain ballistic transport in a device?

I would like to know the ballistic device characteristics and illustrations (if any) to understand how can we overcome the dependence of current on carrier mobility .
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Why is the diffusion capacitance greater than the depletion capacitance in a p-n junction?

In a p-n junction the total capacitance is the sum of depletion capacitance and diffusion capacitance and it is mentioned that the diffusion capacitance is almost a million times greater than the ...
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Why is effective mass of holes positive?

i am trying to understand this. I know that the effective mass of electrons or holes is calculated as: $$m^* = \frac{h^2}{(4\pi^2)\frac{d^2E}{dk^2}}$$ Now,if i look at this plot for example: I ...
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270 views

Semiconductor problem: how much Boron is required to establish a certain amount of charge carrier density

The problem description is as follows: Boron is used to dope 1 kg of germanium (Ge). How much boron (B) is required to establish a charge carrier density of 3.091 x 10^17 / cm^3. One mole of ...
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If we connect a block of p-type semiconductor only to a positive terminal, will it become positively charged?

Connect the positive terminal of a battery to a piece of p-doped semiconductor, say, silicon doped with boron. Will the terminal pull electrons out of the doped silicon, or equivalently, inject holes ...
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why some elements of same group cannot be used for doping semiconductors?

15th group elements like As, Sb, P can be used for doping whereas N and Bi cannot be used for doping even though they too belong belong to 15th group. Why ?
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When recombination in PN junction occurs, which atom becomes an ion?

In an unbiased PN junction, when the carriers recombine to form a depletion layer , it is said that immobile ions are formed. We know that the conduction band electrons in N type are not associated ...
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Optical absorption in a semiconductor for $E<E_g$ [duplicate]

Quoting from Solid State Electronic Devices (by Ben G. Streetman and Sanjay Banerjee): A photon with energy less than $E_g$ is unable to excite an electron from the valence band to the ...
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313 views

How do High Electron Mobility Transistors (HEMT) work?

I am studying High Electron Mobility Transistors (HEMT), but I simply cannot understand how they work in the way described by the references I've read on the Internet. This is what I understand so ...
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How to check the ohmic contact to the film?

I have a thin semiconductor film deposited on an isolating substrate. I would like to check different metals to find out do they form the ohmic contact or Schottky barrier. What is the best way to do ...
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How can we determine the inbuilt barrierpotential and electric feld for a given band diagram?

Suppose I have got two p type silicon materials of different concentrations (the difference in thier concentrations is small but considerable enough that their fermi levels differ by noticeable ...
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Semi-conductors

Suppose there is a semiconductor with Fermi energy $E_f$ and that there are $N$ bound electron states. I'd like to know why the mean number of excited electrons takes the form $$\bar n={N\over ...
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53 views

How should semiconductors be understood? [duplicate]

In the chemistry setting, a doped semiconductor is a crystal lattice with holes/extra electrons in it. In the band/quantum mechanical picture, these holes/extra electrons can be seen as the amount ...
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45 views

Diffusion and Drift currents in a PN junction

In a forward-biased PN junction, the potential barrier decreases, allowing more majority carriers from one side to diffuse to the other side where they are minority carriers. After they cross the ...
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Can the current in a semiconductor be independent of mobility of charge carriers?

Can any device be made in such a way that the current through it is independent of carrier mobility? In a usual semiconductor or a device which is made of semiconductor material the current due to ...
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Schottky Barrier - Why energy band levels at interface are assumed to remain the same that bulk

I have been chewing up some time ago the Schottky-Mott theory of Schottky Barrier height (which ignores the surface states). All the deduction seems to ground on fundamental thermodynamical principles ...
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What is the performance of a silicon crystal that makes it an essential component to computing

I'm on a thread of interest in the precise physics that allow the creation of the computing process. It began as a question posted in search of an understandable explanation of what physical form ...
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P-N junction voltage under polarization

All the books that deal with the p-n junction under applied bias asume that the same equations used for the equilibrium case (no bias) can be used for the biased case provided that the juntcion ...
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How can doped semiconductor be neutral?

I have studied about the two types of doping which result in p and n type semiconductors. I also came to know that they are neutral. But, how can it be? Is it that the positive charge(holes) in ...
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Semiconductor doping and conductivity

Why is the conductivity of Si dopped with P and As much bigger than the conductivity of Si dopped with In and P?
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What are the differences between supperlattices and Multiple Quantum Wells Semiconductor Structures?

Semiconductor Optoelectronics: What are the differences between multiple Quantum Wells and supperlattices.
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Why does a window layer is on top of the absorber layer in solar cells and not below it?

In solar cells there is a p-n junction. P-type semiconductor (for example CdTe) is often absorber layer because of its carrier lifetime and mobilities. In case of CdS/CdTe, CdS is n-type window layer ...
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Calculating band gap from band structure

If while calculating a band gap, the band just below the Fermi level touches the Fermi level, can we say the material is semiconducting?
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Sold-State Band Structure - connection between Fermi Energy, Fermi Level and Work Fuction

I've been struggling with the concepts of these three terms - Fermi Energy, Fermi Level and work fuction. Now, I was given these definitions (in the context of semi-conductors): Fermi Level is the ...
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Can zinc nitride be used as light emitting material?

I cannot manage to find any journal papers about the applicability of zinc nitride as active layer of an light emitting diode (LED). But certain papers got mention that zinc nitride with a direct ...
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73 views

Rms value of rectified output from a half wave rectifier

The rms value of an alternating quantity which is the input to a half wave rectifier is $\frac{I_{max}}{\sqrt2}$. Then the rms value of output should be $\frac{I_{max}}{2} \sqrt 2$. But it is given ...
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Why can electricity flow only in one direction through a diode?

A few days ago I was soldering a small thing which contained a diode, a battery and some other useless things. Unfortunately, I soldered the diode reversed and it didn't work. When I reversed it ...
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Alignment of Fermi Levels between Metal and Insulator

If I stick a metal and insulator together, will the Fermi level of the metal align with the insulator? When people draw a band diagram for a metal-oxide-semiconductor heterostructure, I never see ...
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118 views

Effective mass of a particle

I was reading about concept of effective mass on Wikipedia and came across the line that effective mass of a particle can be negative and even zero. How is this possible?
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Optical mode leakage through a layer of gold

The geometry of my semiconductor device is given below. The blue regions are gold, the grey ones - gallium arsenide (n-doped to $2.9 \times 10^{15} \mathrm{cm^{-3}}$). The dimensions are μm, i.e. it ...
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74 views

List of experimental band gap

does anyone know where one can find a list, database, book of experimental bandgap values of semiconductors? Is there such a collection? Or do I need to scour papers one at a time to get the values?