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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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Difference between diode and LED

What is the difference between a diode and a led? I know a led is a diode and I know how they are used and so on but I'm not really sure why a regular is not also light emitting. Therefore, what is ...
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Resolve The Envelope Detector Circuit

I was working on a little project and I was wondering if the envelope detector circuit could be resolved analytically. Let me explain. The circuit is the one shown above, I know the values of $C$, $R$...
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Types of effective masses

I understand the existence of effective mass for electrons, light hole, heavy hole, and split-off. But how can they be different from the density of states effective mass of conduction and valence ...
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Why don't rectifiers deplete the AC source of electrons? [on hold]

As I understand it, the most simple rectifier can be made by attaching a diode to an AC source, only allowing half the wave form through, and then adding a capacitor to smooth it out. Then, the end of ...
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Gamma spectrometry

Suppose I have a sample containing only 137Cs. Now assume it shows 100 cps counts for 137Cs, 662keV energy. Now I added 60Co (1173, 1332 keV) source in the same sample. Compton scattering ...
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Questions regarding germanium detector

Why n+ contact in n type Ge is not several hundred microns? . Why we require both additional p or n type contact? in p type Ge, why we require additional p type junction also? crystal itself should ...
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NPN transistors reverse biased

How is a pn reverse bias junction is formed in a NPN transistor? In a normal pn diode during a reverse bias junction an 'internal battery ' is formed which counteracts the movement of electrons . But ...
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In which region of diode breakdown starts?

i confused about in which region of a diode breakdown start, in some books it is given that breakdown starts in depletion region but in some other is said that it start in p-side or n-side of diode (...
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During formation of PN junction which electrons diffuse through junction

during formation of pn junction electrons from n type diffuse to p type material .electrons jump across junction but which electrons jump to fill holes on p side i mean conduction electrons or valance ...
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Splitting of energy levels in solids [duplicate]

when atoms are well seperated energy spectrum is discrete, but when they come together energy levels split and they form bands, upto this i can understand. where im confused is that these splitting ...
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What is a “space-charge”, in the context of photodetector non-linearities?

I'm going back and reading all these papers from a few decades ago regarding detector nonlinearities, and they talk a lot about space-charges and the space-charge field, but not one paper I've found ...
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Why n+ contact of p type Ge is 700um thick compared to p+ contact of n type Ge only 0.3um?

Whether the reason is as follows? Predominantly HPGe is p type. So compensation of large p type impurity requires more n+ contact. (700um) But n type Ge is made by doping of excess addition of n type ...
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Diffusion stopping current?

In the forward bias when electrons enter the p-type region of the semiconductor, the charge concentration is increased, and since the movement of electrons is faster than the movement of holes, it ...
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PN Junction diode depletion width [closed]

depletion width formula of a pn junction diode has V(barrier)-V(external) i.e if the barrier potential is 0.6v(say) and i apply a forward voltage of 1V, then as per the calculation Width becomes ...
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on diffusion process in semiconductor devices

Consider a PN junction. Say that the P and the N sides are just brought into contact and the diffusion process has started. We say that as the diffusion occurs, the charge carriers leave behind ...
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Schrodinger equation in momentum representation with position-dependent effective mass

I'm trying to convert Schrodinger equation with position-dependent effective mass (PDEM) to momentum representation, and I'm not sure how to apply the kinetic energy operator. In position ...
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Quantum Mechanical Tunneling in a Resonant Tunneling Diode

I am currently trying to simulate a Resonant Tunneling Diode (RTD) on a somewhat basic level, so the question is rather general. Quantum-mechanically its structure is shown well in this figure: Two ...
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Chemical potential in a simple semiconductor

I came across the following problem in my undegrad solid state physics book: Assume a semiconductor with two bands, the lower band is defined as $E(k)$ and the upper band is defined by $E_0 - E(k)$ ...
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Semiconductors/insulators: Why is the fermi energy between the valence and conduction band?

Ive asking myself a question on the fermi-energy. The fermi-energy is defined as the maximum energy which an electron, following the Pauli-rule, can have at T=0. In semiconductors and insulators the ...
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Relation between intrinsic Fermi level and electric field

If I consider a semiconductor in equilibrium (type P or N, non uniformly doped, 1D situation), how can I express the electric field in terms of the intrinsic Fermi level? I am trying to approach this ...
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Working of a photodiode

I am reading photo diode and I have couple of questions in. So my understanding of a photodiode is that these are devices which consume electricity and produce light So if that being the case, I am ...
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Why can blue LEDs be used for generating white light, but red LEDs cannot

LEDs consist of pn-junctions, so why can blue LEDs be used for generating white light, but red LEDs cannot
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How does acceptor impurities lock down electrons in a semiconductor?

I think n-type semiconductors are easier to understand. You have an atom with 5 valence electrons, 4 of them are used up to connect it to the lattice and the remaining 1 electron needs only a little ...
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Finding the carrier concentration of semiconductor

Silicon (4 valence electrons) can be doped with arsenic (5 valence electrons) to make an n-type semiconductor. Assuming 1 in every 15 million silicon atoms is replaced with arsenic, calculate the ...
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Question about built in voltage in p-n junction

If I have two materials, joined together to make a p-n junction, the $V_{bi}$ is found by calculating the difference between the conduction bands or LUMO levels. Should this be the same as the ...
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Why does diode built-in voltage persist when current begins flowing?

When P and N type semiconductors are connected together, some of the electrons drift from the N type into the P type to recombine with holes. This leaves positive ions on the N type and negative ions ...
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Why does the depletion region shrink in a forward biased p-n junction diode?

I was studying about semiconductors and I came up with a doubt in my mind . Let us assume a p-n junction diode is in its steady state in unbiased condition that is no charge is flowing through the ...
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Can Einstein relation be used to calculate mobility under equilibrium dynamics?

In weak field non-equilibrium dynamics, mobility can be calculated by Einstein relation $\mu=\frac{eD}{K_BT}$, where $D$ is diffusion constant. Mobility can also be calculated by the definition $\mu=...
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Attempting to calculate the mobility from SCLC measurement (space charge limited current)

I performed an SCLC measurement on a p-type material (hole transport layer) for a solar cell. Referring to the wikipedia page:https://en.wikipedia.org/wiki/Space_charge The relationship between $J$ ...
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Is it possible for the charge carrier concentration to go down when doping?

Not sure if this makes sense, but if a p-type material is doped with another p-type material, is it possible for the hole concentration to go down, or will it always increase?
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Further doping p-type material. Why doesn't this increase the hole mobility. etc?

I did a project in which I made perovksite nanocrystal solar cells. The hole transport material was doped with another p-type material and performance was compared. It turns out that this didn't ...
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1answer
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Is there a simple rule connecting all indirect semiconductors band gaps to their electron-hole pair generation average energy?

The band gap of Diamond, Silicon and Germanium is 5.5, 1.12, 0.66 eV while the average energy to produce an electron-hole pair for the same semiconductor is namely 13, 3.6 and 2.9 eV. This ratios are ...
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Width of depletion region in P-N junction [duplicate]

Hello I wanted to ask how the width of the depletion region in reverse biased condition changes with the external voltage source
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Reversed biased condition np junction

Well there are a few posts about the reverse biased condition but I have a problem understanding one thing. Why doesn't current flow in reverse biased diode? It the picture there are positive ...
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Is metallic hydrogen an example of exciton?

I know that in exciton an electron is excited and goes from valence band to conducting band leaving an electron hole which is positively charged, soon Jupiter came into my mind and then this question. ...
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Which heat equation should I choose if I want to toggle between conductive and convective heat transfer?

I have a science project where I have an aluminum cylinder, filled with oil, with a diode chain floating inside of it. The diode chain has a bimetallic temperature switch on it that turns off the ...
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1answer
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At what pressure do semiconductors break down? [closed]

So let's say you were going to send some electronics to the bottom of the ocean, 3-5km down. This would be about $5km*1000kg=5Mkgf/m^{2}$. So at what pressure do circuit boards, transistors, etc stop ...
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Mobility of electrons and holes

According to experimental results it has been found that in Silicon holes are one-third as mobile as electrons. But if doping is considerably low such that phonon scattering is dominant over impurity ...
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leakage current as a function of the depletion width

How does the leakage current behave with an increasing reverse voltage applied to a semiconductor? Will it increase too or is it independent from the depletion with respectively voltage? I can argue ...
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1answer
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Why is Zener breakdown of a PN junction reversible but avalanche breakdown irreversible?

I have read in my textbook that if a PN junction is in Zener breakdown and if we now reduce the external voltage, the PN junction is not damaged and returns back to its initial state. However, the ...
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1answer
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Fermi-Dirac Function

Why do we assume complete ionization of donor energy level (any doping level) even if we know that when Ef will be closer to it, the probability of electron finding will increase? Context- ...
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Characteristic curve of a solar panel

I have trouble understanding the $I(U)$-plot of a solar panel: So without any light it should probably just be the characteristic curve of a diode, right? Which means that at some point, when the ...
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What is the difference between a dielectric and a semiconductor?

It would be very nice if you could give an equation to discern the two material classes. Please do not provide an answer which is based on the band gap size, since in the last years also diamond (...
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1answer
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What is a pump reflector?

I understand the meaning of laser pumping. But i don't understand what is a pump reflector. As a clear definition does not appear online. In the paper,DESIGN AND DEVELOPMENT OF WIDEBAND HYBRID RAMAN/...
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1answer
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What is the binding energy between conduction band and valence band of metals and insulators?

As far as my understanding of solid state physics goes, I can't see a clear connection between binding energy and band gap. But our teacher asked us the question as an assignment but i really can't ...
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Can a semiconductor become more conductive than a conductor with heat?

I am looking for a good idea for a science fair project for PA Junior Academy of Science (PJAS). An interesting idea that I have stumbled across is making semiconductors more conductive with heat. I ...
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Thermo-electric current in the p-type semiconductor

I came across this picture : Source:thermo-electric generators Basically, within the p-type semiconductor, I don't know how holes move from the hot side to the cold one. How does this happen? If ...
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1answer
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Are there any other bands except for valence band and conduction band in any material?

When atoms or molecules are brought together to form a lattice, outermost orbit electrons gain discrete energy levels and when these energies are classified they group into valence band and conduction ...
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Can Hall Voltage be used to glow a bulb?

The voltage developed along the semiconductor i.e perpendicular to magnetic field and current flow be used to glow a bulb? When hall voltage develops what happens to potential drop across the ...
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Why does the depletion layer of a p-n junction diode decrease in width upon forward biasing?

The current in the direction of intrinsic diffusion increases, as the potential barrier decreases. I'm okay with that, but I feel that the dip in potential barrier has nothing to do with the width of ...