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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Is it possible to excite a semiconductor @ k=0?

Let us assume a direct semiconductor with parabolic band structure around the $\Gamma$ point (which is not bad for most semiconductors) in momentum ($k$) space. Now we excite it with light: I ...
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What can justify the decrease of the electrical conductivity with the increase of light intensity?

I have currently been working with a sample that "appears to" decrease its resistance when I cover it and protect it from light. Basically it presents the opposite behaviour of a photoresistor. What ...
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250 views

Why are there direct bandgaps?

This Question has been bugging me for sometime. Some semiconductors have direct bandgaps and indirect bandgaps. So what causes a direct bandgap to occur? The physics behind ,why there are direct ...
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82 views

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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173 views

How bandgap engineering works?

Currently i am reading about bandgap engineering in zinc oxide. I read that using external dopents likes magnesium or cadmium we can increase or decrease bandgap of zinc oxide,thus giving unique ...
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182 views

Doped semiconductors

I have a quick question I hope someone can answer. Why do you dope a semiconductor ? Is that only to get more carriers to conduct, or is it also to make the energy gap between the valance- and ...
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104 views

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 ...
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What is Si-delta doping? [closed]

I want to know what the delta means in this case. I know the Si means the element used, by some way to doping. I guess the delta means that using some elements to create holes in semiconductor made ...
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121 views

Does the Black's equation work for immortal wires / interconnections (or only for mortal ones)?

I'm trying to understand whether the Black's equation is only true for mortal wire / interconnections or it is also applicable to immortal wires (essentially when its $jL$ product is less than ...
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21 views

Where does the reverse current come from in a organic semiconducting diode?

Unlike traditional inorganic diodes, organic semiconducting materials hold few thermally exited free carriers under room temperature, so the reverse current should be small if pinholes of the films is ...
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332 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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2answers
93 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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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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Why do electrons in graphene behave as Dirac fermions near the Dirac points?

I've been learning about graphene, and I recently calculated the band structure for it using a nearest-neighbor tight-binding model for the $\pi$ electrons: $$\varepsilon(\vec k)=\pm t\sqrt{3+2 \cos ...
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2answers
173 views

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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132 views

Layered CMOS structure question

I am trying to understand the workings of a CMOS image sensor. I understand that increasing wavelength results in an increased penetration depth in the silicon often used in CMOS image sensors. What ...
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1answer
90 views

weight of fully loaded RAM

I had read a post Is a hard drive heavier when it is full? It states, there is some difference in the weight of fully loaded hard drive and an empty hard drive due to different orientation of ...
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2k views

Is it viable or possible to make your own transistor?

Just wondering if it is possible/viable to construct your own transistor, not small like todays, but the same scale as the one created at Bell Labs.
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287 views

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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2answers
739 views

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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1answer
171 views

Are $A$ and $J$ in Black's equation (for electromigration reliability of wires/interconnections) independent?

Black's equation is an empirical model to estimate the MTTF (mean time to failure) of a wire, taking electromigration into consideration. Since then, the formula has been getting popularity in ...
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2answers
807 views

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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1answer
779 views

Constructing Tauc Plots

How can we construct a tauc plot using data from the transmission spectra? How does one calculate the absorption coefficient for plotting tauc plots?
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285 views

Influence of the temperature on the ionization energies for impurities in silicon

Is there any dependence of the impurities ionization energy on temperature in silicon? I mean if there are any interactions between localized electron and phonons which leads to renormalization of ...
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236 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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306 views

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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637 views

How did the Bardeen-Brattain point-contact transistor work?

How did the Bardeen-Brattain point-contact transistor work? What are the conditions under which a Schottky barrier injects minority carriers? In a bipolar junction transistor the forward-biased ...
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2answers
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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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369 views

Photon Absorption and Emission: Conductors v. Semiconductors

I'm having a hard time understanding how photon absorption and emission in metals (conductors) compares to semiconductors. Obviously, in SCs, absorbed photons lead to electron-hole pairs and emitted ...
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218 views

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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153 views

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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491 views

Estimation of the internal electric field strength in the pn-junction

I would like to compare my result in an order of magnitude. So, How can I estimate the strength of the electric field in a typical Si PN-junction?
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2k views

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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327 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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763 views

Fermi and Boltzmann distribution of carriers in semiconductor

What are the requirements for describing charge carriers (e.g. electrons) in a semiconducting material by - Fermi distribution - Boltzmann distribution When do we apply the one or the other? If 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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420 views

Electrical conductivity of an intrinsic semiconductor

On which factor does the electrical conductivity of an intrinsic semiconductor depend? It doesn't have an excess of charge carriers in fact, does it?
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490 views

Can electrons move through vacuum?

I studied that electronics is the branch of physics which deals with the practical applications of moving electrons through vacuum, semi-conductors and gasses. Can electrons move through vacuum?
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252 views

What limits the maximum attainable Fermi Energy for a material experimentally?

Either through doping or gating. What are some good terms to search for if I'm looking for some experimentally obtained values for particular materials? I'm particularly interested in what the limit ...
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90 views

Electron Relaxation/Polarization for and n-type Semiconductor

Please help me understand the following (general) statement, referring to electrons in a full valence band of an n-type semiconductor: "An electron filling up the last empty state in the valence band ...
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117 views

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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63 views

1 Mohm Resistivity at cryogenic temperature for doped silicon

I would like to pick the correct doping of silicon to get 1 Mohm cm resistivity at liquid helium temperature of 4.2 K. The metal insulator transition implies that I need a very accurate doping. Are ...
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335 views

Carbon in the form of graphite a conductor?

Well, it happens a I have a glucose test strip (One Touch Ultra) which has three electrodes (Counter, Working and Reference) and I'm guessing this electrodes are made from graphite mixed with a ...
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116 views

Why is spectral sensivity of a photodiode expressed in A/W

Can someone explain me the meaning of the A/W unit of the photosensivity when reading a spectral response function of the wavelength characteristic of a photodiode?
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70 views

Semi-conductors and induced charge

Can a semi-conductor ( germanium or silicon) or a semi-metal ( graphite ) carry an induced charge ?
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448 views

Ionized Depletion Region, Why aren't those charged being excited?

Ok so I understand the PN junction, and how when 2 Semiconductor materials are placed together the Electrons will jump into the Holes near the junction creating a Negatively Ionized Atoms on the ...
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381 views

Semi-conductor band-gap and deformation potential

Submitting a semi-conductor to stress leads to a deformation in the energy-bands, roughly described by:$$H_{ij} = {\cal{D}}_{ij}^{\alpha\beta}\;\epsilon_{\alpha\beta}$$ $\epsilon$ being the strain ...
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217 views

Is it feasible to convert the energy of gamma-photons from gamma-emitting nuclear isomers into electrical power?

It is known that gamma rays emitted by nuclear isomers, naturally occurring or manufactured, carry huge amounts of energy. Co-60 for example decays into the isomeric state of Ni-60 by $\beta ^-$ ...
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How local is the stress tensor?

I am confused by the definition of the stress tensor in a crystal (let's say a semi-conductor), I don't see how it could be "more local" than over an unit cell. I know that in field theory the stress ...
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184 views

Carrier Electrons Generation and Recombination Time

When a Electron gets promoted to the conduction band from valence band (In generation) lets say for example in Silicon at room temperature. Is there any way to determine (on average) how long it will ...