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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What are “electron holes” in semiconductors?

I'm tutoring senior high school students. So far I've explained them the concepts of atomic structure (Bohr's model & Quantum mechanical model) very clearly. Now the next topic to be taught is ...
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Effect of doping on the width of depletion layer of PN-junction diode

I've read that if there is very low doping in a pn-junction diode, the depletion region will be large because a large volume of depleted semiconductor is needed to generate enough electric field to ...
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Why doesn't current flows in reverse biased diode?

Consider this reverse biased diode : I read that no or very small current flows in reverse biased diode as depletion layers get widened and huge resistance is offered so no electrons can cross it. ...
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Reverse bias P-N junction [duplicate]

I am not able to understand why the PN junction does not conduct when reverse biased. Can't electrons travel from the N side through the power supply to the P side where they can jump from one hole to ...
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Why absence of electron is called hole?

I am having hard time in understanding the concept of holes: If there is no electron than how can it be a hole? For a moment lets assume absence of electron is termed as hole but how can this absent ...
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Holes in a P-type semiconductor under external force E

Basically in almost every semiconductor texts, there will be all these concepts concerning electrons, holes, dopants, fermi-levels. However, I have been always confused about the picture of hole ...
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Charge density in depletion layer for pn-junction

I just came across this Wikipedia article on pn-junctions: pn junction What I don't get is why the negative charge density is narrower/smaller than the positive one in Figure A. I'm guessing the ...
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Pn junction voltage drop?

This image from wikipedia, explains that there occurs a potential drop across a pn semiconductor junction, and an electric field confined to the depletion region. I already know the reason for the ...
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Would HgTe be a topological insulator?

In "Quantum Spin Hall Insulator State in HgTe Quantum Wells", researchers observed a 2D topological insulator by sandwiching HgTe between CdTe. Is the CdTe really necessary? Would Vacuum/HgTe/Vacuum ...
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What does the Fermi Energy really signify in a Semiconductor?

In understanding the behavior of semiconductors, I'm coming across a description of the Fermi Energy here and at Wikipedia's page (Fermi Energy, Fermi Level). If I understand correctly, the Fermi ...
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Why isn't there a potential difference across a disconnected diode?

I know this question sounds silly, as if there was a potential difference a current would be created when the terminals are connected together and this would mean energy has come from somewhere. The ...
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243 views

Semiconductors and localization of the electrons

When looking at the band diagram of a semi-conductor, direct conclusion of the invariance under discrete translations, for a filled state with an electron, one does know precisely it's momentum, so my ...
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The skin effect and the reflectivity of gold

I am simulating a waveguide in COMSOL, a FEM solver. My model looks like this (it is similar to a standard Quantum Cascade Laser geometry): Therefore there is a very thin (30nm) layer of gold ...
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Tunneling v. Hopping

Can someone explain the difference between hopping and tunneling? The context I'm considering is conduction in semiconductors, specifically between impurity states within the bandgap. It's always ...
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What the heck is negative effective mass?

I am reading this book:Solid State Electronic Devices by Ben G Streetman and Sanjay Kumar Banerjee. I have some doubts in the article 3.2.2 Effective mass. In this the aythors say that ...
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440 views

Fermi level in equilibrium and non-equilibrium situations

Why do the Fermi level for electrons and holes coincide in equilibrium condition and why do they separate as quasi-Fermi levels in non equilibrium situations?
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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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In solar cells, do photons break apart electron-hole pairs, or create them?

Some sources say that when a photon hits the PV cell, it breaks apart electron-hole pairs. Other sources say that photons create electron-hole pairs. Can anyone explain which one is right? I've read ...
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112 views

Spin FET Transistor

Spin FET Transistor. When a gate voltage is applied to a current of spin polarized electrons, a spin precession will occur. If this spin precession is enough to make the bulk electron spin ...
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102 views

Need an intermediate resistivity part/material

I need a part or material for a planned experiment (the experiment is similar to those described in my articles http://arxiv.org/abs/1208.0066 and http://arxiv.org/abs/1109.1626 ). The problem is that ...
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How does current flow from the emitter, through the base and to the collector in a NPN transistor?

So, I understand that for a NPN transistor to work the emitter-base junction needs to be forward biased and the collector-base junction needs to be reverse biased. I understand how current flows from ...
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PN Junction Depletion Region

So it took me a little bit to understand this, but I want to make sure I have a few things right. First of all, when a Crystal Structure with One side N-Doped, One Side P-Doped are in the same ...
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Why does the conductivity $\sigma$ decrease with the temperature $T$ in a semi-conductor?

We performed an undergrad experiment where we looked at the resistance $\rho$ and Hall constant $R_\text H$ of a doped InAs semiconductor with the van der Pauw method. Then we cooled it down to around ...
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How do Zener diodes maintain the potential across their terminals?

My physics book has a topic about Zener diodes being used as voltage regulators in the reverse bias. Well, I'm curious to know how does a Zener diode maintain the potential across its terminals after ...
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Depletion region

In a semiconductor diode. There is a depletion region formed, it is formed when electrons from n type side migrate to p type side, now which electrons transfer? Valence band ones present at the ...
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Working of a p-n junction diode when forward biased

If p-type semiconductor and n-type semiconductor of a diode are equally doped, and if the diode is forward biased, then holes will move toward the n-type semiconductor and electrons will move toward ...
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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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Why are there two quasi Fermi levels and only one Equilibrium Fermi level?

I am reading a book and I'm trying to understand the concept of quasi Fermi levels. For example, A steady state of Electron Hole pairs are created at the rate of $10^{13}\ \mathrm{cm}^{-3}$ per ...
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63 views

What determines the forward voltage drop for a diode?

I have always had the idea that the forward voltage drop in a semiconductor diode was related in a simple way to the bandgap energies in the semiconductor. However this is apparently not the case: ...
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What is the difference between the Franz-Keldysh effect and free carrier absorption?

What is the difference between the Franz-Keldysh effect and free carrier absorption? My first guess to this is that the Franz-Keldysh effect involves a bandgap potential of non-zero volts D.C. while ...
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61 views

Why can solar cells be made of indirect and direct semiconductors? (Comparison between some pn-junction devices)

Various textbooks mention, but not go into detail, how semiconductor devices are optimized for their particular function. E-k space is trascendental to understand this, given that it depends on the ...
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123 views

Why is titanium dioxide transparent for visible light but not for UV?

I wonder the reason for TiO2 thin films to be transparent for visible light but not for UV. I made a quick search and I found that it is due to the band gap of TiO2. It absorbs UV light but not ...
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448 views

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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155 views

In an avalanche breakdown, where are the electrons that break free from?

In an avalanche breakdown, are the electrons that break free under the influence of the applied electric field from the depletion region or outside it? Also, under reverse bias, how exactly is the ...
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302 views

DFT for bandstructure

Density Functional Theory (DFT) is not appropriate in predicting the band gap of the materials. However, which functional gives close value to the experimentally observed band gap of semiconductors? ...
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In the diode equation, why the exponential $\exp$ and the ideality factor $n$ are there? What do they represent & what is their significance?

In the Shockley diode equation, why the exponential $\exp$ and the ideality factor $n$ are there? What do they represent & what is their significance? I have to work on Solar Photovoltaics, and ...
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Current through the reverse biased junction in transistor [closed]

A transistor is a three terminal device. One terminal is called emitter, one collector and in between them is base. Now, during biasing the junction between emitter and base is made forward biased and ...
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55 views

Internal Resistor in a Diode

When we talk about the resistance of a diode (of the P and N region), is this resistance like the one inside an Electro-Motive Force or it acts like a normal resistor (external electric field exist)? ...
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intrinsic concentration of charge carriers

In case of semiconductor the intrinsic charge carrier concentration N, always remains constant. This explains the decrease in number of holes when donor impurities are added to an intrinsic ...