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 harness it in electrical circuits.

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Fermi Level: chemical potential vs. electrochemical potential

In solid-state physics it is understood that the Fermi-Level is the electrochemical potential. The Fermi-Level is defined to: However, in thermodynamics this formula is referred to as the ...
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Extremely forward biased pn junction

When a pn-junction (e.g. an LED) is forward biased the height of the potential barrier is reduced... ...unless you apply a huge potential $V$, in which case the barrier gets inverted and the band ...
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Silver vs Aluminum electrodes in silicon solar cells?

In a typical high efficiency solar cell, silver is used as a front contact and aluminum as the rear contact. Despite the lower resistivity of silver, the usage of aluminum as a front contact would ...
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PMOS Gate Oxide Capacitance Equation?

I'm having a hard time finding the correct equation for the question shown below. Any ideas on which one I'd need? I've seen this equation: I understand that $\varepsilon_{ox} = \varepsilon_r ...
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34 views

Doped PNP Bipolar Transistor

When doping a PNP bipolar transistor, does it matter which parts are doped by what amount? The picture below will show my question. Am I right in saying that the Emitter is connected to one P region, ...
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How can a phosphorous ion dope silicon when it is already ionized?

In ion implantation dopant ions are directly bombarded into the semiconductor (silicon for example)? But if say P ions (P+) were implanted then it does not have an extra electron to donate into the ...
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Working principle of CIGS solar cells

can anybody explain me how CIGS solar cells working.when photon hits the window layer is there any EHP created or ,that buffer layer lets pass photon energy to absorber layer.please explain me by ...
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CIGS Photo Voltaic cells

Why n type layer is on top of p type layer in CIGS solar cells? does it do anything with wavelength of photon and thickness of window and absorber layer?
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22 views

Calculation of RMS current in half wave rectifier

While calculating RMS current in half wave rectifier, why we will consider only half wave that means only we consider the limits 0 to pi. But here RMS current is for AC input..so why don't we consider ...
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Are there measurable quantities which directly depends on the Fermi velocity?

The dispersion relation of electrons in, for example, graphene exhibits Dirac cones. The dispersion relation of a Dirac point at $\mathbf{k}=\mathbf{K}$ is linear in the momentum magnitude: $$E=\pm ...
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Does doping and size determine the characteristics of a semi-conductor?

Does the maximum voltage and current that a semiconductor can withstand (without being damaged) depend upon the size and doping of the semiconductor? If so, then please explain, 1.What is the reason ...
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What is the smallest possible electronic transistor?

Computers have increased in processing power mainly due to the miniaturization of transistors. I read recently that IBM, with great difficulty, shrank circuits from 14nm to 7nm but progress seems to ...
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Why the optical gap is not identical to the charge gap?

The optical gap is the photon energy required to create an exciton (in a solar cell for example). The charge gap (aka electrical gap) is the energy (voltage) required to create a photon (in an LED for ...
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Why is Fermi-Dirac type of distribution used in semiconductors?

We assume that distribution of electrons follows Fermi-Dirac distribution / statistics in semiconductor model which will help to find the concentrations of electron and holes and the relationship ...
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What causes this IR emission in UV 365nm LED?

I've just got access to spectrometer and measuring spectrum of everything. But when I took a look at 365nm UV led from chinese UV flashlight I got something really strange - it had some IR at exactly ...
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Spin-orbit coupling of low band gap vs large band gap semiconductors

Why do low band gap material III-V semiconductors, like InAs, show a spin orbit coupling effect higher than large band gap semiconductors? Please give me some references if possible.
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Nature of photoluminescence at a semiconductor heterojunction

Do I understand it correctly that photoluminescence at a semiconductor heterojunction occurs because of intralayer recombination? If so, why can't photoluminescence occur because of interlayer ...
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40 views

Why do semiconductors remain neutral outside the depletion region?

Why there is a sharp cut off of the charged region outside the depletion region, like on this image? For example why don't electrons on the conduction band in the n-type side rush towards the ...
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Why does normal incidence eliminate the photocarrier effect radiation in this experiment?

Here's a paper in which they use GaAs crystals at a few orientations to produce THz radiation, by means of Optical Rectification (OR). That's actually not what this question is about, though. They ...
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Adding thin films to a Peltier Device

I am using a peltier device maintaining a constant gradient by applying a voltage/current. My current setup is: Cold Side Peltier Device Hot Side CPU fan Was just wondering forgetting time ...
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Is the electron-hole pair a 1D quantum oscillator or 3D oscillator

I'm trying to use fluctuation dissipation theorem to describe spontaneous photon emission process by electron-hole recombination in semiconductor material. I notice that all the references using such ...
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32 views

what is the source of nonlinear behaviour of semiconductor transistor?

It is known that semiconductor transistor can be used as a switch as well as amplifier. How does the linear amplifying characteristic and non-linear switching characteristic come in a single system?
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e-e scattering rate in normal fermi liquid and in graphene

In Ashcroft/Mermin's solid state physics, in equation (17.64) they argued that: We expect from lowest-order perturbation theory (Born approximation) that $\tau$ will depend on the ...
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Why are band maxima / minima often (always?) at high-symmetry points?

(inspired by this question.) In every semiconductor that I can think of, the valence band maximum and conduction band minimum are at a high-symmetry point in the Brillouin Zone (BZ). Often the BZ ...
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How does phonon scattering change the distribution function?

For a one-dimensional structure, we know that the modified distribution function has the following energy dependency in equilibrium: \begin{equation} Z(\varepsilon)\,f(\varepsilon) = ...
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Can I catch a single photon with webcam's CMOS or CCD sensors?

I thought it would be nice to capturing single photons using a webcam's sensor due to simplicity. I've read that ccd and cmos sensors have a certain percent of quantum efficiency. What about ...
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Reverse recovery current + diode

The reverse recovery current of a diode is due to accumulated charges in the P and N region during it forward stat. I want to know this current is a diffusion current or a drift current?
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Relationship between Fermi Energy and Average Energy

Electrons are in a one dimensional box of length 2L. What is the relationship between Ef, the fermi energy and E, the average energy? The answer is Ef/3 I looked up the formula for the relationship: ...
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Interpretation of the diode constant in a LED

For a real diode the current as function of the potential difference between its terminals (for big enough voltage) is given by: $$I=A e^{\frac{eV-E}{\eta k_B T}} \tag{1}$$ So in the case of LEDs ...
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Is $\kappa_e$ caused by charge-carrier transport or electron transport?

$\kappa$ usually symbolises thermal conductivity, a material's ability to conduct heat. $\kappa$ can be expressed with other partial thermal conductivities: $\kappa=\kappa_e+\kappa_{ph}+...$ where ...
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When do optical phonon branches arise?

As far as I understand from what I'm studying, only when you have more than one kind of atom in the lattice structure, will the phonon have an optical branch, or else it should not have an optical ...
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Can you dope insulators

The question came in my mind because of the definition of doping. For p-type we create holes just above the valence band. This creates holes in the valence band which can contribute to conduction. ...
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Smallest theoretical process node for ASIC

This is just a curiosity question but I remember when 90nm seemed insane so I was wondering what the theoretical limit would be on process size before we couldn't go any smaller. Wiki tells me that ...
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Barrier potential for germanium, silicon and gallium arsenide

Where did the barrier potentials for Germanium (0.3V), Silicon (0.7V) and Germanium Arsenide (1.2V) come from? How was it derived?
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Help with the analytical solution for the dispersion relation of an elastic wave with wave vector k

I was studying Phonons and Lattice vibrations and came across the equation. I want the mathematical solution for this. $$M\frac{d^2u_n}{dt^2}=C[u_{n+1}+u_{n-1}-2u_n]$$ from here it is argued that ...
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Why in excitation in indirect bandgap materials photon absorption is always before phonon absorption?

Why is it always photon->phonon? Why can't it be phonon->photon? (source)
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For an intrinsic semiconductor, why is fermi level half-way? [duplicate]

Why is the fermi level half-way between the conduction band and valence band?
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Relation between energy band gap and atomic number

Is there any relation between energy band gap in group4 elements and their atomic numbers? It might be just a trivial observation but I noticed How from Carbon to Germanium the band gap went from ...
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Are there electrons in the electron energy levels that are created due to doping in N type semiconductors?

I was going through this article.There it is mention that The addition of donor impurities contributes electron energy levels high in the semiconductor band gap so that electrons can be easily ...
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Can the Fermi energy lie into the band gap?

Fermi energy $\rightarrow$ highest energy level filled at $T=0K$ Fermi level $\rightarrow$ Energy level where we have a chance of $50\%$ to find an electron. Now in my course text they say that for ...
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How is a semiconductor electrically neutral?

I'm in the process of learning how transistors works, which starts with understanding how doping is used to create n-type and p-type semiconductor materials. All the resources I read sort of explain ...
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When doping a material, why is As called impurity?

Doping is the act of adding impurities to Group-IV elements to e.g. improve their conductivity. Though it is improving the conductivity, why is it called impurities?
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electric potential at the other end of diode

I was brushing my basics about diode & got stuck at a point...my question is Consider a diode let the positive terminal of the diode be connected to +ve of battery Now in the figure let the ...
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Semiconductors light emission

Suppose a pure semiconductor, with a direct gap. If I apply a constant voltage to it the electrons will jump to the conduction band. So when I turn it off will it emite light?, because the electrons ...
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Resistance & temperature of semiconductor

From what I have read about semiconductors, the reason their IV characteristic shows a decrease in resistance is because as voltage is increased, current is increased. However, the reason for the ...
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Do holes have physical existence?

We know that holes are created due to electrons hopping from one covalent bond to another. But does a hole have a physical existence or it's just a fictitious positive charge, an illusion created by ...
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Concentrations of carriers in semiconductor

For a given semiconductor at a given temperature $T$ with doping levels of acceptors $N_A$ and donors $N_D$ and intrinsic carrier concentration $n_i$ without any external biases, how can I calculate ...
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Combining a p and n type semiconductor

According to my textbook, when a p and n type semiconductor combine the following happens: Electrons from the n type semiconductor will migrate into the p-type semiconductor at the junction (so the ...
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How do the Fermi level, HOMO and LUMO change with doping?

I am a bit confused about solid state physics of organic materials because as I know the workfunction changes with the doping of a material but the Fermi level is constant with doping. So depend on ...
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Steady State Solution for Carrier Concentration of Intrinsic Silicon in an Electric Field

I'm trying to model carrier action in intrinsic silicon under an applied electric field in one dimension. Taking $n$ and $p$ to be the concentrations of electrons and holes respectively, I got that ...