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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Why defects don't have an effective charge in metals?
In semiconductors and insulators, crystal defects, e.g., vacancies and interstitials, are treated as having an effective charge. In metals, however, defects are treated as neutral. I can expect that ...
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A question related to shift in the Fermi energy [closed]
If the effective mass of holes in a semiconductor is 5 times that of the electron, at what temperature would the Fermi level shift by 15% from the middle of the forbidden energy band? (given that, eg =...
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How to Properly Discretize Semiconductor Continuity Equations
I am looking to perform numerical modeling of a MOSFET device and am wanting to better understand how to discretize the semiconductor continuity equations. The semiconductor equations consist of the ...
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Using Jacobi Method for Solving Full Semiconductor Equations
I am looking to perform modeling of a MOSFET device and have therefore been researching computational methods for how to do so. Quite often when solving the Poisson equation, the reader is pointed to ...
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Solid state devices, hole current [duplicate]
why do we consider hole movement as well as the electron movement in the total current term, the hole movement is the effect of the cause (electron movement), so how can they both contribute total ...
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Finite Difference Modeling of MOSFET Device
Does anyone know of any references for MOSFET modeling done using the Finite Difference Method that they could point me to? I understand the gist of the operation, namely using Poisson's equation to ...
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Why does an electron hole have a positive charge in semi-conductors?
From the link below, they explain when an electron in the valence band is promoted to the conduction band it leaves behind an electron hole. But in the case of the image below, we can see when Si is ...
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Is spin relaxation asymmetric in magnetic semiconductors?
I am considering photo-excitation in magnetic semiconductors (e.g. metal organic frameworks). The cartoon picture is like this:
where there will be a spin polarization in the conduction band since ...
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How is the number of charge carriers set free in an x-ray detector proportional to the energy of the incoming photon?
I'm a chemistry undergrad student and I've been doing some research into the ways light is generated and detected at different parts of the spectrum (for the purposes of better understanding practical ...
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Difference between the numerical values of the intrinsic carrier concentration $n_i$ in silicon
I've been working on the intrinsic carrier concentration for silicon, and if calculated with the formula
$$n_i = \sqrt{N_vN_c}\exp{\left(\frac{-E_g}{2kT}\right)}$$
taking the accepted values $N_v \...
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Semiconductor-graphene-semiconductor junction
In the literature, I've found Graphene-semiconductor junctions are treated as Schottky junctions. So by reverse-biasing a graphene n-semiconductor junction, we inject carriers into the graphene ...
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Why do dopant levels lie in the energy band gap of semiconductor?
Dopants create impurity levels in the band gap, this is what we were taught in semiconductor classes. And indeed that's what's seen in experiments (for example https://www.globalsino.com/EM/page2777....
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How can red LEDs still give a faint glow at a voltage of only 1.4V? [duplicate]
How can a red LED work at a voltage of only $1.4{\rm V}$? Red photons have an energy of $1.77{\rm V}$ if we use $\lambda = 0.7\mu\text{m}$ in the relation:
$$ E = \hbar \omega = \frac{2\pi\hbar c}{\...
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How does the Fermi level of graphene change if it is placed in a biased pn junction or in a plate capacitor?
I ran into a problem on which I can't really find any solutions in literature. I am looking at a Graphene sheet that is sandwiched in a biased pn junction (current flows orthogonal to the Graphene ...
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Graphene dispersion at Dirac points
After deriving the dispersion relation of graphene:
$$ E(k) = \pm t \sqrt{3+2\cos{(k_y \sqrt{3} a)} + 4\cos{\bigg(\frac{3a}{2} k_x \bigg)} \cos{ \bigg(\frac{\sqrt{3}}{2}a k_y \bigg)} } $$
how do I see ...
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Why would a depletion "layer" form in a PN junction?
I understand that electrons diffuse from the N to the P region due to the concentration difference. This diffusion of electrons creates an electric field opposing further diffusion.
What I don't ...
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Where can I read about excitons?
I'm having a tough time finding a good reference for excitons. I know next to nothing about them, and I'd like to find a good book/paper/notes that would introduce it in a slow, pedagogical way. ...
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How do solar cells really work?
When I read articles on the workings of photovoltaics, the explanation tends to revolve around the idea of PN-junctions, and how an electric field separates charges (electrons and holes). In a Quora ...
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Thermal Smearing in Josephson Junction
I'm basically trying to simulate a josephson junction at a particular temperature. As per some of the plots I could find, the rise in temperature leads to a rounding of the I - V curve. I was ...
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Resistively and Capacitively Shunted Junction (RCSJ) Model of Josephson Junction Numerical Solution
I'm trying to write a program to plot the I-V charateristics the josephson junction using a python program for some given values of resistance $R$, capacitance $C$, and critical current $I_0$, using ...
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Why do we need to consider interaction for doping atom?
In semiconductors, the intrinsic carrier concentration is calculated by Fermi-Dirac distribution, but for the situation of doping, we need to consider the Coulomb interaction for doping atom, and the ...
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Fermi-Dirac integrals of different orders
Which physical quantities are related to the Fermi-Dirac integrals of different orders?
If fermi-dirac integral, write like this:
$$F_\xi(\eta_c) = \frac{1}{\Gamma(\xi+1)} \int_{0}^{\infty} \frac{x^{\...
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Does diffusion current "consume" thermal energy?
My (possibly erroneous) understanding of solid state physic has led me to the belief that diffusion current may "consume" thermal energy.
Here is my (possibly erroneous) understanding. When ...
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Doping density dependence on effective density of states Si pn junction
I would like to know how the doping density influences the effective density of states in a pn junction. For example the classic relations used to determine this is
$$N_c = 2\left(\frac{2\pi m_n^* k_B ...
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Connecting semi-conductors to outside wires
I know about semi-conductors, and https://en.wikipedia.org/wiki/Schottky_diode .
Question is: how is a transistor or a more complex semi-conductor wired to the metal outside without accidentally ...
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C$_{60}$ fullerene electronic structure, C$_{60}$ insulator
I read a post on Chemistry stackexchange, how to explain that C$_{60}$ is an insulator. The common ground seemed to be that -- in contrast to graphene -- a C$_{60}$ solid consists of separate ...
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Intrinsic band gap vs work function of doped semiconductors
I'm confused about this question on doped semiconductors:
Question: Photoelectrons with a maximum energy of $\ 0.5$ eV are observed when light of wavelength
$500$ nm is incident on a heavily n-doped ...
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How exactly does a p-n junction operate when biased by current *not* voltage?
I'm trying to understand on the Fermi-level of the P-N junction, what happens when I bias a diode via an ideal current source ? I understand how the energy levels behave when biased via voltage source,...
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What is the relationship between the applied reverse bias in a p-n junction to the band gap of the semiconductor?
Consider a p-n junction under reverse bias. The difference in the Fermi Energy of the p-side and the n-side is $qV_r$ where $q$ is the elementary charge, and $V_r$ is the applied reverse voltage. What ...
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Electromotive force by PN junction and extraneous role of electrolyte in electrochemical cells
When the two semiconductors N and P are connected, because of higher Fermi energy, electrons migrate from N to P so that an electric filed is formed in the depletion region (attached picture) which ...
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Shockley Equation works better at higher temperatures
I have been doing some work as part of my undergraduate labs, and currently, the experiment is to determine the constant $e/k_B$ from the I-V response of a germanium PN junction. However, I've ...
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I don't really get transistors. How do they work exactly in the active region?
So in an NPN transistor, when the base-emitter is forward biased, and the base-collector is reversed biased, electrons from the emitter get to the base. That part I understand, electrons are the main ...
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Can doping significantly decrease a monolayer semiconductor's band gap to almost metallic levels?
I am currently an undergraduate student tackling DFT calculations on my 3x3 CsGeBr3 perovskite monolayer with Fe-doping and Biaxial Straining using Quantum Espresso thru BURAI. I have found out that ...
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Current Inside the Depletion Region Forward Biased PN Junction
For a forward biased PN junction, we assume the hole and electron currents are constant inside the depletion region when there is no generation or recombination in the depletion region (shown from the ...
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How can charge neutrality be maintained for a forward-biased PN junction?
When a PN junction is forward biased, majority electons diffuse into p region and majority holes diffuse into n region, if we impose quasi-neutrality, then we have that in the p and n regiosn the ...
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How can i calculate dangling bond density of Si plane?
I've researched how to calculate number of dangling bonds in Si plane (100) , (110), (111)...
I can't figure out how to approach.
Is there any way to do so?
I searched one report that in FCC structure ...
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Built-In Potential (Forward vs Thermal Equilibruim)
According to my book the built-in potential $V_{bi}$ for a PN junction under thermal equiliubrium is:
$$V_{bi}= \frac{KT}{q}In(\frac{n_{no}p_{po}}{{n_{i}}^2})$$
where $n_{no}$ and $p_{po}$ are the ...
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Would a diode more ideal than Shockley diode equation violate the second law of thermodynamics?
The Shockley diode equation describes the behavior of all diodes extremely well. Semiconductor p-n diodes and Schottky diodes are described by the very same equation. Furthermore, it applies to light ...
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Electric Field Far From PN Junction
According to Semiconductor physics and devices Book by Donald A. Neamen book. The electric field far from the space charge region is very small and most of the applied voltage happens across the space ...
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Current due to Ambipolar transport of excess carrier in semiconductors
I am reading Neaman's textbook and I am confused by the ambipolar transport phenomenon. According to what I have understood, if excess carriers are injected somehow into a doped semiconductor piece, ...
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Minority-carrier only injection into bulk semiconductor
If an n-type bulk semiconductor sample was injected from the side with holes. Such that holes are injected uniformly into a small region near the side surface of the sample. Does this excess minority ...
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Effect of any one dysfunctional diode in a bridge rectifier
In these bridge rectifiers what if a diode becomes like fully dysfunctional, and stops conducting totally in a direction. I was wondering if the output voltage will be like a half wave pulsating DC? ...
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Plotting curves of diode current against temperature
I have done I-V measurement at different temperatures on a diode, now I am trying to plot the $I_D$ vs temperature curve but varying $\eta$ (the ideality factor). I am not sure of the procedure though....
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Carrier Recombination Lifetime in Thermal Equilibrium
All the books I read talk about carrier recombination lifetime when the semiconductor material is pushed out of equilibrium. But let's say the material is in equilibrium ( where generation and ...
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How to determine the effective mass for multivariate dispersion relation? [duplicate]
Consider the 1D dispersion obtained by the tight-binding method:
$
E(k)=\epsilon_0-t\cos(ka)
$
$\epsilon_0$ is the on-site energy and $t$ is the hopping energy. To find the effective mass, you can ...
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How to calculate the diffusion length in modulation doping?
I have read a paper(dx.doi.org/10.1021/nl201206d) about an application of modulation doping in bulk thermoelectric materials, in this paper, the nanoparticles diffuse carriers to the host materials, ...
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Is the drift current of minority carriers negligible in the continuity equation?
When deriving the ambipolar transport equations for an extrinsic semiconductor under low injection, I have found certain discrepances between different references.
For instance, in Neamen's ...
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Fermi Level Shift in PN Junction
The image below shows the Fermi level shift of the PN junction when the potential of the N region is positive with respect to the P region. My textbook (Semiconductor physics and devices by Donald A. ...
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Change in internal chemical potential of electrons in the 2DEG
I was reading about quantum capacitance and came across the following formula:
$$\Delta \mu = \frac{N}{\rho}$$ where N is the number of electrons moved from the metal to the low-density-of-states ...
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Phonon and the coupling to electrons
I am new to looking at phonons, especially in relation to their use in coupling to electrons.
Phonons can be defined as the treatment of vibrations in a crystal lattice. There can be different types/...
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