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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How to design over voltage protection Crowbar Circuit? [migrated]

I'm designing a Crowbar over voltage protection circuit with following specifications, Maximum input voltage - 30V Maximum input current - 5A Output voltage - 5V Output current - 5A So I have ...
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What is the effect of dopant on the crystalite size?

Crystal size decreases with doping and then increases with increase in dopant concentration, why? the ionic radii of dopant is greater than the host atoms.
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creating eh-pairs in a semiconductor -> conduction or valence band?

When a beam ray respectively a photon creates an electron-hole pair in a semiconductor, e.g. for silicon the ionization energy is 3.6 eV, is the electron then directly in the conduction band? So does ...
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Why is silicon absorbing visible light?

Here it is shown that silicon absorbs visible light: but the band gap energy for direct transitions is 3.6 eV which does not match to this absorption coefficient. Instead, the band gap energy for an ...
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38 views

Why is the necessary energy for a photon to lift an electron higher than the band gap energy?

The band gap energy of silicon is around 1 eV and though the required energy for a photon to lift an electron up into the conduction band is around 3.6 eV. Why is this? Is the Energy of an absorbed ...
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23 views

Why is the Fermi level (energy) shfited in doped semiconductors?

According to the Fermi level is shifted due to doping: Upwards in case of n-type and downwards in case of p-type. Why is this? The Fermi level is the level where the probability that an electron ...
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Why is the carrier distribution / density of states different in doped semiconductors?

How can it be explained that the carrier distribution is different in case of doped semiconductors? I understand it naturally, that the distribution of electrons is higher for n-type semiconductors. ...
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29 views

How many photons will a scintillation crystal emit?

The question is already in the title: How many photons will an excited scintillator emit? It is probably mainly given by the energy of the impinging particle and the bandgap energy. But also probably ...
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MOSFET I - Vg curve [closed]

Below graph shows the I - Vg curve in the subthreshold region, Quadritica region, and linear region for 5 different transistors. I was asked to determine which I - Vg curve in the below graph is ...
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MOSFET Band Diagram from surface to substrate [closed]

The question below asks to identify the band diagram of MOSFET at different Vg. This band diagram is drawn from oxide-silicon surface to silicon substrate. my understanding is that the band diagram ...
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$C$-$V$ characteristics of MOS capacitors for different material [closed]

For C-V curve below for 3 different materials, (Si, InAs, InSb). What material will be corresponding to curve A/B/C? My understanding is that C is inversely proportional to the dielectric constant in ...
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P-I-N Semi-Conductor Cell Efficiency [closed]

I am working on this home work problem (See graph below), asking which curve I/V has higher efficiency. Question 1 : My understanding is that cell efficiency is related to Isc * Voc * n, How could I ...
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Electromagnetic wave and skin depth, skin effect

In EM theory concept of skin depth is induced which is a measure of how much a EM wave can penetrate the medium, from it arises the concept of skin effect which is for EM wave but we use this to ...
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Method for making graphene plausible?

Gallium does not wet quartz or graphite. I’m pretty sure graphite doesn’t stick to quartz (or not well) especially if smooth. So what if on a round flat plate of polished fused quartz you set a small ...
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Why are there positive charge in $SiO_2$?

Why are there positive charges in material SiO2 for a PN junction? Apparently, this creates an accumulation of electrons in the substrate.
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Why irradiation could invert the type of a given doping in the subtrate of a PN junction

Does it happen for subtrate P and N ? Why for the two types ?
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In semiconductor physics, in context of PN junctions/pixel detectors, what is the difference/meaning of N-in-N and N-in-P technology?

In semiconductor physics, in context of PN junctions/pixel detectors, what is the difference/meaning of N-in-N and N-in-P technology ? How could we have a N-N diode ?
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Combined effects of strain and doping on the electronic structure of semiconductors

I've read papers in DFT studies on band gap tuning in semiconductors and the usually studied methods are either through doping or application of external strain. But its always just one or the other. ...
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Find electron-hole recombination rate? [closed]

In an n-type semiconductor, the thermal equilibrium electron concentration (n0=1015/cm3) and the intrinsic carrier concentration (ni=1010/cm3). The mean life time of minority carriers is 1us. The ...
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Distance $E_F-E_i$ in a compensated semiconductor

Given two energy level diagrams for a compensated conductor: At $0~\text{K}$ At $500~\text{K}$ I want to determine for which diagram is the Fermi level closest/farthest from $E_i$. It's a ...
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applied voltage on n-typed semiconductor changes its carrier lifetime

An apparatus was constructed in the lab to measure charge carrier lifetime. An LED illuminates an n-typed germanium semi-conductor with a square function with a constant frequency (the period of the ...
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1answer
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How can one determine the key characteristics of a solar cell from the I-V curve?

I have recently measured the IV characteristics of several Si solar cell samples and am now attempting to extract the series resistance $R_S$; parallel resistance $R_P$; open circuit voltage $V_{OC}$; ...
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1answer
59 views

How is quantum physics translated into the world of electronics? [closed]

I remember watching a documentary about early works in quantum physics and how it was essential to the microelectronics revolution and the invention of the transistor. What part exactly helped? Is ...
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1answer
30 views

Does semiconductor laser need stimulating photon to produce coherent light?

In regular laser, we need: stimulating photon => this makes the output light coherent ways to make inversion population resonant cavity in the pictures about semiconductor laser, I do not see any ...
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Fano factor measurements

I am looking for information on the measurements of the Fano factor, in particular in germanium. Does anyone know accessible papers?
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What happens when electron keeps hitting on a metal plate

In SEM, in order to 'focus' the electron beam, an aperture is used (which usually is metal); what happens to the metal after so many electron hits the metal constantly? since metals are usually are ...
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Fermi level in metals and semicoductors

As we read about Fermi energy, it is the energy of the highest occupied electrons. But if we look at the energy level diagram of semiconductor the Fermi level is situated somewhere between the valence ...
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1answer
29 views

The n-type dopant elements on silicon

The n-type dopant elements on silicon are phosphorus, arsenic, and antimony from the group V elements. My question is that what is the difference between doping P, As, or Sb? How do we decide to dope ...
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Temperature influence on Hall Effect for semiconductor

Currently, I'm taking a course in modern physics experiments and last week I was asked to study the hall effect in a semiconductor. One of the experiments was with a germanium chip where a steady ...
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1answer
24 views

How does one obtain a semiconductor's absorption coefficient from first principles?

Is the absorption coefficient of a semiconducting material at a given wavelength obtainable from the material's band structure? If so, how? Are there any pedagogical papers you could recommend to help ...
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1answer
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Conceptual question regarding transistor biasing

I know that in a transistor, the base-emitter (B-E) junction has to be forward biased while collector-base (C-B) junction needs to be in reverse bias. Question: What would happen if we alter this ...
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24 views

Half wave rectifier confusion

I am searching for a good book or link or video that might give some fresh idea about half wave rectifier properties I mean in my book prescribe by my university that has introduced some of the basic ...
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Is activation voltage the sum of voltage required to collapse depletion layer and band gap energy?

Is the energy released when an electron moves from the valence to conductance band states the activation voltage or is activation voltage the energy required for electrons to overcome the depletion ...
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1answer
48 views

How do electrons exit LEDs? Aren't they in the valence energy state?

If a conducting electron reduces to the valence band in an LED, where does it get the energy to go back to the conductance band upon leaving the diode so current can flow? I'm confused as to how ...
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Why n and p are not additive in law of mass action? or Why is the sum of electron concentration and hole concentration is not constant?

I was asked this question during a viva examination. I tried to give answer through mathematical derivation but I was told to give the answer from intuition. So why is $n_0 p_0 = n_i^2$, and not $n_0 ...
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19 views

Simulation of QW gain

For a student project, I need to compute and plot the gain of a semiconductor quantum-well. In my case, I am interested to reproduce the results from Schwartz et al. (Investigation and comparison of ...
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24 views

Electrical properties of the Wannier exciton

We know that excitons are charge neutral and doesn't show any electrical properties, but is it the same for Wannier exciton too? For example, if a Wannier exciton placed in the electric field, can it ...
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1answer
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Why there is no reabsorption in LED crystals?

Can you explain to me please, why there is no reabsorption in crystals which are used as LEDs? Because the energy of emitted light is the same as the band gap of the semiconductor - it should be ...
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1answer
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Question about the purpose of a transistor [closed]

I've been studying about diodes and transistors and something made me wonder about the purpose of transistors. In the examples we were talking about increasing current by using two batteries with a ...
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22 views

Half-wave rectifier output graph

I want to know what will be the output V-t graph when you connect a half-wave rectifier to a battery using an inverter instead of a traditional AC source? Because when I tried it, the output graph ...
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Semiconductor and temperature dependence

Does the conductivity of both intrinsic and extrinsic semiconductor increases with temperature or is it that conductivity of extrinsic semiconductor decreases with temperature just like a conductor ?
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Electronics and junctions

In a p-n junction, is it only the electrons that move from the n-type part to the p-type part in order to create a depletion region or is it the movement of both electrons and holes from the n-type ...
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How insulators and conductors were discovered?

I know Stephen gray has discovered insulator and conductor. But I want to know that how did he know which one is conductor and which one is insulator ? Please tell me the details how had he done that ...
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Why does the base-emitter voltage in NPN transistor become constant

The setup above shows the experiment that I have been working with. During the experiment, the current $i_c$ and the voltage $V_{be}$ were measured for increasing $V_{in}$. At some point, the current ...
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1answer
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Resource recommendation for spintronics

What are some good beginner level books to understand spintronics. I am looking for some sources in which basic mathematics of spintronics is properly explained.
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Which statistical distribution could be assumed for the mobility of Silicon substrate material?

Mobility is a key parameter for Hall elements or in transistor models. If we measure the mobility on Si wafers, then we can expect some variation from die to die or sample to sample. Which statistical ...
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1answer
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Is this photodiode-based “energy harvester using the coldness of outer space” just based on established thermoelectric effects?

I've read through the explanation and can not understand what they are saying in terms of the underlying physics. My hunch is that this is a demonstration of a well established thermoelectric effect ...
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What is the definition of a bipolaron and a dipolaron?

I wondered about the exact definition of a bipolaron? In particular, if I have an oxygen vacancy in a metal oxide and the 2 excess electrons (when forming a neutral oxygen vacancy) localise on the 2 ...
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Upper State Lifetime vs Exited State Lifetime vs Gain Recovery Time

Could any one explain differences between these three terms about semiconductors and semiconductor optical amplifiers.
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Density of states in 1D semiconductor

I'm given the dispersion relation for the energy band of my semiconductor: $E(k)=\alpha+\beta\cos(ka)$ where $a, \alpha, \beta$ are know parameters and I must obtain the density of states from that. ...