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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Voltage and Fermi levels

It is well known that the voltage $V$ across, say, a p-n junction can be related to the electro-chemical potentials (usually and improperly called Fermi levels) at the borders of the junction $$ qV = \...
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Model for a thin metal/semiconductor junction?

Are there any books or articles that describe models for transport in a metal/semiconductor junction where the thickness of the semiconductor is less than the thickness of the depletion/accumulation ...
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How does annealing improves the ohmic contact?

Suppose we have a p-type material and metal contacts deposited taking the work function of a metal and semiconductor into account. At room temperature (depending on the doping level) they might now ...
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1answer
653 views

Why is an exciton only observed when we excite to the conduction band and not to other electronic level inside the bandgap?

Excitons can be observed when we excite electrons to the conduction band. I don't know about excitons being observed when we excite the electrons to an electronic level that would eventually be in ...
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Why bulk of HPGe detectors is doped?

When I am looking at schematic diagrams of HPGe gamma spectrometer detectors (like this Ortec GLP one), it is often mentioned that bulk of Ge is doped. In this example - P-type doped. Is there a ...
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33 views

Books recommendation to understand Quantum Confined Stark Effect

I am starting a PhD on a photonic component involved with QCSE. The problem is that I have a Master degree in electronical engineering, not in fundamental physics, and I need to understand the QCSE in ...
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1answer
327 views

Potential drop across PN junction diode in forward bias

If a PN junction diode is connected to a battery, the P part must have a higher potential than the N part(because these points are connected to the battery) and so there should be a potential drop ...
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1answer
65 views

Different Color Intenensities from simple ON/OFF RGB subpixels

I recently got interested in electronic paper. One design that I liked was the one from Mirasol: https://en.wikipedia.org/wiki/Interferometric_modulator_display However, what I don't understand, is ...
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What is a Fermi arc?

What is meant with a Fermi arc in the context of Weyl semimetals? Is this the just a one-dimensional Fermi surface? For example, in electron-doped graphene, the Fermi surface consists of 2 disjoint ...
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1answer
81 views

Conductance of an interacting quasi one dimensional wire using the method for a 1D Fermi gas?

Assuming the electrons are non interacting and spin degenerate, the conductance of a quasi one dimensional quantum wire is quantised in units of $2\frac{e^2}{h}$. For small voltages, we simply count ...
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Is Making a laser diode at a home workshop impossible?

I love to play with laser diodes and they have always been a fascinating thing for me. Usually, I play with $0.1$mW laser diode pointer (Which are just toys) . From some physics textbooks and videos , ...
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Studying Chaos in RLD circuit

We are currently working on non-linear dynamics (chaos theory) by analysing a series circuit including a diode (the 1N4004), a 100 ohm resistor and a 20 mH inductance. It is driven by an alternative ...
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Reconciling electron configuration and valence electron distribution over separate energy levels in energy band theory

This seemed like more of a chemistry question to me, but I was told by the people at chemistry.stackexchange that it might be more appropriate to post here, since "it was the physics guys that did all ...
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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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276 views

“Doping” a metal

I had my practical exams today, where I was told to explain the structure and working of a Unijunction transistor (UJT, https://www.daenotes.com/electronics/industrial-electronics/ujt-uni-junction-...
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Optical Conductivity and Scattering rate - Physical intuition

Why does the real part of conductivity increase with increase in scattering rate at frequencies much larger than the scattering rate? I understand the mathematical implication, but do not understand ...
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1k views

How to calculate Hall coefficient in gold and silver?

BACKGROUND - Hall Effect Using the free-electron model, the Hall coefficient is calculated as $$R_H = \frac{1}{ne},$$ where $e$ is the elementary charge and $n$ is the carrier density. For a metal $X$...
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What do I measure with power meter?

I modulate directly a laser diode by setting the pump current periodically from 0 A to $I_{on}$ A. I do it for different duty cycles and different frequencies. But I need to keep my average power of ...
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192 views

Two-Band k.p Model is not Hermitian for imaginary wavevectors

In E. O. Kane's original work on Zener Tunneling, he uses a two-band $k\cdot p$ model for the semiconductor bandstructure: $$H=\begin{pmatrix}E_g+\frac{\hbar^2k^2}{2m_0}&(\hbar/m)kp\\(\hbar/m)kp&...
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Two Photon Absorption dependence on Semiconductor Band Gap

It's well known that Two Photon Absorption coefficient is scaling with $E_g^{-3}$. Does anyone know what is the physical reason for this scaling? What is the physical theory behind this mathematics?
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211 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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Why does Seebeck coeffcient increase with Temperature?

So I have extracted a graph for the Seebeck coefficient vs energy with at varying temperatures (Top right). However, I am struggling to understand the relationship. Why is it the increase in ...
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1answer
69 views

Why Cannot Photons Create Electron-Hole Pairs?

My question might be dumb or considered trivial, but I will try to explain my confusion. In a Particle Physics course, we were taught that only charged particles (such as electrons $e^{\pm}$, $\mu^{\...
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What's a typical lifetime for excitons, or biexcitons?

I've read that a typical lifetime for excitons in a semiconductor is 1-10 picoseconds. I believe these are Wannier-Mott excitons. What are typical lifetimes of other kinds of excitons, for example in ...
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Apart from mirrors, what other feedback mechanisms can you think of in a semiconductor laser

Today, I was asked by my professor this question. I was unable to answer it but I am curious to know about this. Apart from mirrors, what other feedback mechanisms can you think of in a semiconductor ...
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Effective masses of GaAs-lattice-matched InGaAsP, using k.p method or else

For numerical simulations, I need the effective masses of electrons, light & heavy holes, and split-off carriers, in GaAs-lm InGaAsP. Alternatively, I am considering using the k.p method to ...
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2answers
39 views

Bound states on a Quantum Dot and Tunneling on and off the Dot

Question is essentially: How can the states on a quantum dot be bound when we can tunnel onto them? If plane wave states can tunnel onto them, these plane waves states and the 'bound' states will have ...
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Why does Ashcroft and Mermin say an acceptor level in a semiconductor cannot be empty, only singly or doubly occupied?

On page 581 of Ashcroft and Mermin, Solid State Physics: Acceptor Level In contrast to a donor level, an acceptor level, when viewed as an electronic level, can be singly or doubly occupied, but not ...
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2answers
65 views

If an electron-hole pair is formed, where does the electron “go”?

I've seen the explanation before that holes are basically electron deficiencies in an atom and that the hole "moves around" by electrons from surrounding atoms shuffling to fill that spot ...
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Conductivity of doped semiconductors at absolute zero

We can distinguish semiconductors from metals by saying that metals still conduct at absolute zero whereas semiconductors don't. Does this still apply to doped semiconductors which have an excess of ...
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What is a topological Dirac semimetal?

I have just started learning about a topological Dirac semimetal. Then I'm wondering that the Dirac point always crosses the Fermi energy in a topological Dirac semimetal. If the Dirac point does not ...
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What is an “As-grown crystal”?

I was going through a paper on a material. In that paper the authors mention "as-grown crystal". I tried looking for it on Wikipedia and searched it online but none of them tell what it is. So can ...
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1answer
33 views

Conduction band energy level under illumination

I am new to the field and my apologies if its trivial question. Consider a semiconductor having valence and conduction band at certain energy level. When it is illuminated with photons having ...
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Why is the drift current in a PN junction independent of electric field?

I've learnt that under the forward biased condition in PN junction, the diffusion current increases slowly and after surpassing the cut-in voltage, the diffusion current increases exponentially, and ...
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1answer
1k views

Fermi energy in conduction band while valence band and conduction band have no overlap

I often see band diagrams of of solids and in cases of semiconductors, I often see a band gap separating the valence band and conduction band while the Fermi energy lies in the conduction band like ...
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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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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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Energy of band of $d$-dimensional semiconductor when voltage $V$ is applied across

Let's say we have a one-dimensional semiconductor and I apply a voltage $V$ across it, I want to calculate the energy of a parabolic band, when a source and drain voltage is applied across it. I ...
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141 views

Conductivity of a heavily doped semiconductor at Absolute zero temperature

As the Fermi level moves toward the conduction band in an n-type semiconductor; when heavily doped, it moves into the conduction band of the semi conductor. So, will the semi conductor behave as a ...
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1answer
355 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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Please grant me an accurate explanation of diode reverse bias mechanism

Consider the image above. Now I am an electron in that depletion region. I was not here initially, I was in the wire (free-moving electron of a copper atom) or perhaps battery (...of an ion?) but now ...
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Do carriers move across a p-n junction at $0\ \mathrm{K}$?

Often a band diagram is used to explain what happens when two pieces of the same semiconductor, one p-doped, one n-doped, are put together. I am a little confused about it, so here is my question. ...
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Does the proximity effect in semiconductor/superconductor heterostructures require an accumulation layer

I've recently been looking at literature on the proximity effect in semiconductor-superconductor heterostructures, where the semiconductor takes on superconductivity over mesoscopic distances. ...
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Kinetic energy of electron in Quantum well

I heard that electrons in bulk semiconductor have 3 degree of freedom so they have 3 dimensional kinetic energy component, but Whenever an electron from bulk material captured by a quantum well (where ...
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Are defect levels some eigenvalues of a Schrodinger equation?

When I read this textbook, Fundamentals of defect ionization and transport on the bottom line of page 9, they say that those ionization levels are not eigenvalues of a SE and they're thermodynamic ...
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2answers
479 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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Dead layers in HPGe gamma semiconductor detectors

I have a question about the dead layer properties of HPGe gamma semiconductor detectors. I found this on Wikipedia As of 2012 HPGe detectors commonly use lithium diffusion to make an n+ ohmic ...
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260 views

Energy-band diagrams of heterojunctions

I'm studying heterojunctions and I'm struggling with drawing their energy-band diagrams. I've been looking for books or something to look up how the diagrams can turn out to be with different types of ...
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1answer
5k views

Energy-band diagram of forward-biased pn junction

When a p-n junction is forward biased then its energy-band diagram looks like this: What would happen if $V_a>V_{bi}$? ($V_{bi}$ is the built-in potential and $V_a$ is the externally applied ...
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704 views

How Does Silicon Surface Barrier (SSB) radiation detectors work?

I'm dealing whith some old detectors (about 1980) called Silicon Surface Barrier, searching online I've seen that they consist on metal-semiconductor(Si n-type) junction (schottky diode) and in one ...

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