Questions tagged [semiconductor-physics]

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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Dielectric constant or permittivity of metals

I'm wondering what the dielectric constant or permittivity of metals is --particularly copper. Do metals have an infinite permittivity?
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Two Photon Absorption dependence on Semiconductor Band Gap

It's well known that Two Photon Absorption coefficient is scaling with $E_g^{-3}$. Does anyone know what is the physical reason for this scaling? What is the physical theory behind this mathematics?
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Quantum Cascade Laser [closed]

I want to learn about quantum cascade laser in a six month time. Can anyone please suggest me any reading materials or video lectures. I have background in calculus and linear algebra. I am learning ...
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Why does silicon have an indirect gap?

Is there an intuitive explanation as to why silicon has an indirect gap? I have heard that this can explained using pseudopotentials.
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III-V semiconductor compounds - band gap approximations

I'm looking for the most common and accurate approximation functions for III-V semiconductor compounds. So far, I found two (InGaAs as the sample compound): The simplest one: $E(Ga_{1-x}In_xAs)=(1-x)...
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Where does the labelling of extrinsic semiconductors as “n” and “p” come from?

The naming of doped semiconductors as "n-type" (for donor-doped) and "p-type" (for acceptor-doped) is ubiquitous. But I am having a hard time digging up where this naming tradition comes from and how ...
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Taylor approximation in physics

In a textbook about semicoductor physics, I came across a passage about deriving the carrier concentration at thermal equilibrium in semiconductors I didn't quite grasp: The recombination $R(T,n,p)$...
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Band gaps: are they at the centre or at the edge of the Brillouin zone?

Reading about electronic band structures, I came across the following: Band gaps open at the edges of the Brillouin zone (BZ), since that is where the Bragg scattering occurs. I am slightly ...
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How does temperature affect a semiconductor band gap?

From this link, I've read that An increased interatomic spacing decreases the potential seen by the electrons in the material, which in turn reduces the size of the energy bandgap. Can this ...
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After a diode start conducting, can you increase voltage across the diode without current change in the diode?

let's answer this question using the example below: Let's imagine an ideal condition, where a 5V ideal voltage source with no internal resistance is connected to a diode, the voltage source can only ...
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Why is the silicon crystalline structure is called cubic?

Silicon has a valence 4 (electron shells: 2, 8, 4), hence having 4 neighbors in the 3D space, which for me should appear as a mesh of regular tetrahedrons, with the Si atoms at the centre. But ...
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Metallurgical Junction

I've been studying p-n junction. Then came the term "Metallurgical Junction". What's that? Metallurgical? I know its the study of metals and their properties. But why this is there in semiconductors? ...
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Why a tunnel diode (TD) is called a diode?

Traditionally, a diode is a 2-terminal device that limits current to flow in one direction, i.e. a rectifier. But a "tunnel diode", according to wikipedia, is not rectifying: In the tunnel diode, ...
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Why should the Fermi level of a n-doped semiconductor be below the one of a p-doped?

In a pn-junction, the difference in Fermi level between the p doped and the n doped regions causes the apparition of a built-in electric field at equilibrium. This electric field goes from the n to ...
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Mobility in semiconductors

Good afternoon everybody. I am reading on a book about semiconductor mobility. I have fully understood the definition, but I also noticed that often one talks about high or low mobility. My question ...
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Why don’t illuminated series connected (photo-)diodes bias each other?

When you connect, let's say, three photodiodes or solar cells, with a load, and you measure the voltage across the middle photodiode. Will the voltage change if the adjacent cells are in the dark if ...
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Does the shifting of the Fermi energy level of an intrinsic semiconductor mean that $n \neq p$?

It has been stressed out in the books that I've consulted that, for an intrinsic semiconductor, $n=p$. However, with this in mind, they also derivate the following equation: $$E_{F_i}=\frac{E_c+E_v}{...
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Is there a energy lower to -13.6 eV in a given atom/element?

The Hydrogen atom fundamental energy is -13.6 eV. Is there an atom that has an energy level lower to -13.6 eV ? if no, then why, in semiconductor physics, the integral on energy start at $-\infty$ ...
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Is Fermi level located above or below donor levels in n-type semiconductor?

I find contradicting information about this. Some resources says it's above donor levels Hyperphysics website: and other say it's below, eg. on this ResearchGate thread: in n-type semiconductor,...
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The concept of Fermi level

I have read and used the concept of Fermi level previously and this is simply an attempt on my side to better my understanding of it by asking myself various questions. I understand that the fermi ...
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Why is the exciton binding energy slightly smaller than the band gap energy?

In a semiconductor it requires energy equivalent to the band gap energy ($E_g$) to excite an electron to the conduction band. This gives rise to an exciton (conduction electron-valence hole pair). The ...
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What is a Shockley-Read current?

What is a Shockley-Read current? Googling it brings up nothing. Is it possible this is some obscure name for a type of diode current? I know what the Shockley-Read-Hall process is, is it related to ...
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When a pn junction is formed, why is a positive region of charge formed on the n side of the junction?

I understand that when electrons diffuse from n-side to p-side, negative charge is developed on the p-side. But the mere absence of electrons on the n-side doesn't make that positively charged. The n-...
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Why does overclocking a CPU cause it to generate more heat?

It seems odd to me that overclocking a CPU causes it to consume more energy. The amount of energy flowing through the CPU should be related to the average number of 'gates' (or transistors) that ...
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Which is the best DFT functional for band gap calculation?

Density Functional Theory (DFT) does not predict the correct band gap (E$_{g})$ of the materials. Which exchange and correlation functional predicts the E$_{g}$ value exactly? What about the HOMO-...
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What does intrinsic and extrinsic contribution to Hall effect mean?

In the context of transportation theory (electron and thermal conductivities), what is the physical meaning of extrinsic and intrinsic contributions to the Hall effect (i.e. transverse conductivity)? ...
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Is electron-hole pair thermal equilibrium in semiconductors a dynamic or static equilibrium?

In my textbook, it is mentioned that electron hole pairs in semiconductors are formed due to thermal energy and at a given temperature the number of electrons and holes is constant. The formula given ...
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Confusion regarding the Fermi-Dirac distribution and related formulas

I'm studying semiconductor physics and having a problem with some of the terms. The definition we were given in class for the Fermi-Dirac distribution is: $$f_{FD}(E) = \frac{1}{1+e^\frac{E-E_f}{...
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Why in a conductor increase in temperature makes the atoms vibrate but in a semiconductor the kinetic energy of the free electrons is increased?

When temperature is increased in case of a semiconductor the free electron gets more energy to cross the energy gap to the conduction band from the valence band.so now more electrons can go easily to ...
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Diode IV experiment

Ive been looking at experiments to look at the IV relationship for a LED, but I see most of them use a rheostat instead of a series variable resistor and my question is, what is the advantage of using ...
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Why Silicon band gap energy is more than germanium?

The question is very simple.Why silicon band gap energy is more than germanium at Ok? I know the equation $$EG(Si) = 1.21−(3.6×10-4 )⋅T$$ and $$EG(Ge) = 0.77−(3.6×10-4 )⋅T$$ But what is the physical (...
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How does a work function difference cause band bending in equilibrium in Metal-Oxide-Semiconductor (MOS)?

How does a work function difference cause band bending in equilibrium in Metal-Oxide-Semiconductor (MOS)? I don't understand the physical meaning behind this sentence from Sze: to accommodate the ...
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Flaw in Einstein's explanation of the photoelectric effect?

The essence of Einstein's idea is like this: if a system is in some bound state with energy $-E_b$ with $E_b> 0$ (the threshold of the continuum band is taken as zero), and we drive the system ...
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Conductivity of a crystalline solid

In a crystalline solid each atomic level 'splits' into n levels (n = number of atoms in the system). When the number of atoms is large each level becomes replaced by a band of closely spaced levels. ...
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Silicon atom: How is it replaced by a Phosphorous (or Boron) atom?

My book says: A pure semiconductor at room temperature possesses free electrons and holes but their number is so small that conductivity offered by the pure semiconductor cannot be made of any ...
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Why is more intrinsic carriers bad for high temperature semiconductors?

I'm taking a solid state course, and is currently on the subject of dielectrics. In one of the sections, concerning "Impurities in Dielectrics" the books says: "Impurities can also be used to make ...
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Steady state of diffusion current in semiconductors

Consider a long semiconductor bar is doped uniformly with donor atoms so that the concentration given by $n = N_D$ and is independent of position. Radiation falls upon the end of the bar at $x=0$, ...
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Producing electricity from all wavelengths of electromagnetic spectrum

Is it possible to produce electricity from all wavelengths of electromagnetic spectrum beside visible light ?Like using gamma rays or x-rays .
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In a LED the electrons from the n-type combine with the p-type which creates a photon. Are the electrons 'lost' or gone when this process takes place?

In a LED the electrons in the n-type move to the p-type where they are then 'combined' with the holes in the valence shell of the p-type which produces photons. My question is that when this happens ...
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Hamiltonian of a quantum circuit including a diode?

The LC circuit has a Hamiltonian: $$\hat{H}={E_L\over2} \hat{\varphi}^2 + 4E_C \hat{n}^2$$ where $\hat{\varphi}$ is the magnetic flux and $\hat{n}$ is the number of charge. What is the Hamiltonian ...
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What causes the photoelectric vs photovoltaic effect?

In the photoelectric effect, electrons are physically ejected from the material. In the photovoltaic effect, electrons are knocked out of their atomic orbitals but remain within the material. What ...
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Why do we need pure silicon for a solar cell to be efficient?

Why is it that we need ~99% pure silicon in order to have efficient solar cells? I understand that as silicon purity decreases so does solar cell efficiency but I'd like to understand why.
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How do ceramic thermistors work?

I can hardly find any information.. and the few I got from my script is not revealing so much: Electrons are strongly bounded (ceramics) – electrons are transported from a bound state into an ...
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What is exactly is Crystal Momentum, $\hbar k$?

The title says it all really. Does this mean that the crystal is moving? From my notes, I read that The effect of an external force on an electron in the crystal is to change the crystal momentum $\...
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Why is the channel in the Datta-Das spin transitor a 2DEG?

In the original proposal for the Datta-Das spin transistor, it is assumed that carriers in the channel are a 2D electron gas, as shown in the picture below. Why would a 2DEG form at the InGaAs/InAlAs ...
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Electrons involved in bonding cannot be involved in conduction?

I am currently studying the textbook Physics of Photonics Devices, Second Edition, by Shun Lien Chuang. In a section discussing the basic concepts of semiconductor band and bonding diagrams, the ...
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Finding the Injection Efficiency and IV Characteristics of an LED

I have taken IV measurements for several LEDs and now need to calculate their injection efficiencies. I understand that the injection efficiency: $\eta_{pn} = I_{D}/I$ Where $I$ is the total ...
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Quantum tunneling in zener diodes

Well Zener diodes operate as a voltage regulator because of the Zener effect-Quantum tunneling . Quantum tunneling is the effect when an electron faces an energy barrier but after the energy barrier ...
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Why do electrons move towards a vacant position (hole) in a crystal lattice?

Why do electrons in a crystal lattice move towards the vacant position? Aren't electrons stable in their current position?
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Reverse Biasing of pn junction diode [duplicate]

Why can't the electrons that are attracted to positive terminal of cell flow through the wire ?

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