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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275 views

Can we measure the exact value of the Fermi Level in semiconductor? Or is it always measured relatively to the Conduction/Valence Band energy level?

From the books that I read, the discussion and the formulas related to the Fermi Level are always relative to the energy level of Conduction/Valence Band, or Fermi Level in intrinsic semiconductor. ...
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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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172 views

Electron-hole pair recombination

Please I will like to know if a reasonable amount of heat can be generated upon the recombination of an electron-hole pair in a photo-excited semiconductor nanoparticle (such as TiO2, CeO2).
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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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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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695 views

Hall Coefficient - Is it a constant?

We did a classical Hall Effect experiment where we measured Hall Coef. given by $R_H=\frac{E_H}{J\cdot B}$. The setup was a rectangular Germanium semiconductor placed perpendicular to a magnetic field ...
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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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Shockley's diode equation

We owe a debt to Bell Labs with Shockley, Bardeen and Brattain for inventing the semiconductor. All have now passed on. I remember seeing my first transistor radio in the early 60's. Shockley ...
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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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37 views

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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318 views

Does drift current eventually stop in a p-n junction?

According to the Wikipedia's graph of electric field in a p-n junction, there is no electric field outside the deletion region and hence no minority charge carriers move into the other side. Also, the ...
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Diffusion current density in a semiconductor - A/cm^2?

The units for current density is generally $\frac{A}{m^2}$. One particular equation I'm seeing from a textbook (Microelectronics, by Donald A. Neaman) is: $$J_n=e D_n \frac{dn}{dx}$$ for the ...
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175 views

Extrinsic Semiconductor (N-type)

I'm having trouble grasping the concept of extrinsic/doped semiconductors. For example, suppose that the semiconductor i n-typed with a certain density of donors. At room temperature, about 300 K, I ...
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1answer
122 views

Why an undoped heterojunction causes potential barrier?

In this image (source) a potential double-barrier was created using GaAs and AlAs lattices (undoped). Why would any potential barrier be formed, if all the bonds are electrostatically balanced (i.e. ...
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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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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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119 views

What does it mean if the resistance of a semiconductor increases due to light?

I have synthesized an $n$-type semiconductor material $\text{ZnO}$. Under light illumination, its resistance keeps increasing. What are the reasons for this?
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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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3k views

Does the Fermi level depend on temperature?

I know that this question has been asked before (here and here), but there is still something that I cannot understand: The answers in the linked posts clearly state that the Fermi level (level, not ...
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46 views

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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2answers
118 views

Exciton in semi-conductor

I don't understand why an exciton describes only the interaction between an electron hole and an electron in the conduction band? How is this interaction different from the interaction between an ...
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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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128 views

Why is a substrate needed in growing GaN?

Is the substrate a layer on which GaN crystal grows on? Is there a way to grow free-standing GaN? Would the resultant crystal be full of defects?
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168 views

Output in a half wave rectifier

In a half wave rectifier only a single diode is present. One end of the secondary wire of the transformer is connected to the p side of diode while the other to the load resistor. The n side is ...
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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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298 views

How can depletion region be formed at the center?

Let's consider an electron at the junction in the n-type region. As it moves into the p-type we say it leaves behind a positive ion and hence in this way electrons at the junction in the n-type create ...
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136 views

is there a difference in drift and diffusion under forward biasing in a pn junction?

The current in forward bias is claimed to be because of the diffusion process. However, from what I understand, the diffusion process is being supported by the battery by inducing fields in the ...
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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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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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3answers
42 views

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
209 views

Are Weyl and Dirac points topogical defects in nodal semimetals?

Recently, I heard the Weyl and Dirac points are topogical defects in nodal semimetals. I do not really get it. And the definition of topological defects is confusing to me. Are the topoligical ...
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184 views

How can a photo diode turn its current on and off in nano seconds?

I know that in a photo diode current is carried by minority charge carriers whose concentration depends upon the incident light's intensity. I wonder if incident light has once created electron hole ...
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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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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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5k views

The Gunn diode and the two valley theory

In today lecture of microwave and radar my teacher explained about the Gunn diode. He said it is made up of only one type of matrial e.g. $GaAS$ as shown in (a) part of the image. (source: ...
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220 views

Confused on relation between bandgaps and pn-junction operation

I am an EE not a physicist but I wanted to understand semiconductor operations a little better. I have looked at a couple books on semiconductor physics and I still don't understand the relation ...
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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 ...