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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71 views

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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1answer
543 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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1answer
211 views

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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682 views

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 ...
4
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1answer
73 views

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 ...
4
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1answer
57 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 ...
4
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0answers
958 views

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 ...
3
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177 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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70 views

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 ...
3
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2answers
545 views

Depletion region width in forward bias

In forward bias the electrons from n region move to p region after crossing the depletion region and holes from p region move to n region. But shouldn’t they recombine and hence the width of the ...
3
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1answer
271 views

Effect of magnetic field on energy gap of semiconductors like diode, transistor

I am doing my project on energy gap of semiconductors. For that i have an doubt that what will happen to the energy gap of diode if it is exposed to magnetic field intensity? Is it possible to place ...
3
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59 views

Light - Indium Tin Oxide Interaction

I need to understand the mechanisms behind the light - indium thin oxide interaction for an ITO deposited solar cell. Does it act like a metal or semiconductor? Does it generate electron-hole pairs ...
3
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755 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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122 views

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 ...
3
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165 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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208 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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17 views

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. ...
2
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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 ...
2
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0answers
81 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 ...
2
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1answer
154 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 ...
2
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98 views

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. ...
2
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0answers
79 views

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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79 views

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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40 views

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 ...
2
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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 ...
2
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327 views

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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249 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 ...
2
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76 views

Obtaining a Positive Hall Coefficient for Electrons Near the Top of a Valence Band

Using a Drude model of charge carriers with a charge $q$ and a mass $m$ (which I allow to take either sign at this stage) in a sample with an applied electric field $\mathbf{E}$ and magnetic field $\...
2
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121 views

Van der pauw method for an isolated hole

Van der pauw method is a way to measure the resistivity of a material with arbitrary shape while it meets some specifications ( being homogeneous and ...). One of the conditions is that the sample ...
2
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0answers
1k views

Silver vs Aluminum electrodes in silicon solar cells?

In a typical high efficiency solar cell, silver is used as a front contact and aluminum as the rear contact. Despite the lower resistivity of silver, the usage of aluminum as a front contact would ...
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61 views

Reverse recovery current + diode

The reverse recovery current of a diode is due to accumulated charges in the P and N region during it forward stat. I want to know this current is a diffusion current or a drift current?
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96 views

Interpretation of the diode constant in a LED

For a real diode the current as function of the potential difference between its terminals (for big enough voltage) is given by: $$I=A e^{\frac{eV-E}{\eta k_B T}} \tag{1}$$ So in the case of LEDs ...
2
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1answer
467 views

Reverse Recovery Current of a diode

When the diode is in forward bias phase and suddenly we apply a reverse bias voltage, the diode takes time to be fully blocked because of the excess of minority charges that are stored in P and N ...
2
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812 views

3D Density of states

I have the following dispersion relation: $$\epsilon(\vec{k})=\frac{\hbar}{2}\left(\frac{k_x^2}{m_1}+\frac{k_y^2}{m_2}-\frac{k_z^2}{m_3}\right)$$ (note the minus sign in the third term). And I am ...
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53 views

In k$\cdot$p theory, how does one calculate the bulk inversion asymmetry coefficients given in table 6.3 in Winkler?

In k$\cdot$p theory, how does one calculate the bulk inversion asymmetry coefficients given in table 6.3 in Winkler? Winkler's book on spin-orbit coupling effects is available free online. In ...
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557 views

Effective mass of a particle

I was reading about concept of effective mass on Wikipedia and came across the line that effective mass of a particle can be negative and even zero. How is this possible?
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605 views

More physical explanation of impurity energy levels in a doped semiconductor?

I'm reading about doped semiconductors in Ashcroft and Mermin. They tell you that when donor impurities are added to a semiconductor, their energy level $E_d$ is just slightly below the conduction ...
2
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81 views

generation / destruction of fermions by phonons

my Hamiltonian consists of 1D free fermions coupled to a bosonic bath. The interaction is dictated both by scattering terms $H^{scatt}=\sum_{kq}\alpha^S_{kq}c^\dagger_kc_{k+q}X_q+h.c.$ as well as ...
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142 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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81 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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2k views

Why is the valence band maximum at the gamma point in the bandstructure view of dispersion relation?

Why is the valence band maximum for most semiconductors at the gamma point in the bandstructure view of dispersion relation
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1answer
56 views

How does negative power lead to amplification?

I am currently investigating semiconductor superlattices and I am analyzing the negative differential velocity (NDV) after a certain limit. I understand how NDV leads to negative power, but I am ...
2
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1answer
3k views

What is the reason behind band gap narrowing in semiconductors

I want to know why some semiconductors band gap decreases after doping with elements. Burstein-Moss band-filling effect can be useful to explain band gap widing in a semiconductor materials but i was ...
2
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1answer
443 views

How to check the ohmic contact to the film?

I have a thin semiconductor film deposited on an isolating substrate. I would like to check different metals to find out do they form the ohmic contact or Schottky barrier. What is the best way to do ...
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10 views

Solar cell: Surprising change in EL for varying PEDOT:PSS-thicknesses

I am currently working on improving a solar cell, which is partly transparent and therefore utilizes two transparent electrodes (TCO on top and PEDOT:PSS on the bottom). As PEDOT:PSS alone is not ...
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0answers
22 views

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 ...
1
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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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25 views

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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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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0answers
19 views

Metal Oxide Semiconductor (MOS) Capacitor strong inversion

Why the electron bands in the Body of the MOS capacitor do not bend much futher after the threshold voltage is applied? What stops them from doing it? For reference Modern Semiconductor Devices for IC ...