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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Derivation of Einstein's relation in Drift Diffusion model for Semiconductors

I'm currently reading Semiconductor Devices: Basic Principles by Jasprit Singh. In this book he gives a derivation of the Einstein relation for the Drift Diffusion model of semiconductors, supposing ...
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Electric Field inside a diode

When a voltage is applied to a diode (Forward or Reversed bias) the depletion zone is changed due to charges change in this region. My question is in both case (Forward or Reversed bias), how the ...
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How can I simulate a model electronic hole?

Suppose I can solve time-dependent Schrödinger equation for several 1D particles (currently 3). I'd like to see, what an electronic hole is and how it behaves — in a series of numerical experiments. ...
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In semiconductor devices, why is quantum tunneling “fast”?

I'm reading up on semiconductor devices that rely on quantum tunneling, such as the tunnel diode and the TFET. The big advantage of these devices is apparently that "quantum tunneling is extremely ...
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Mixed Neumann/Dirichlet BCs in Poisson-Schrodinger self-consistent solver

I'm currently in the process of writing a self-consistent Schrodinger-Poisson solver for a device heterstructure (High Mobility Electron Transistor). I am having a few difficulties however. It seems ...
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Simple calculation example of Fermi level pinning at metal-semiconductor interface

I'm having trouble calculating the following example (taken from Jasprit Singh: Semiconductor Devices, Basic Principles; John Wiley and Sons, Inc., 2001; p. 255). "Assume that at the surface of GaAs, ...
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P-n junction diode under forward bias configuration

Why there is exponential growth in current with respect to voltage in p-n junction diode under forward bias configuration?
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What does Fermi level in the band gap mean?

What does it mean that the Fermi level for some semiconductors lie in the band gap? Is Fermi level definition different from what is know as usual? We define the Fermi level as the highest level of ...
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Diode Circuit analysis [migrated]

how can i solve circuits like this ?! how current flow though determine the diode modes and calculate V and current in branches
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Effective masses for different direction

Assume we have an indirect semiconductor where the effective mass becomes anisotropic in different directions. Usually, one talks about a mass in parallel and perpendicular direction referring to ...
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Why should the Fermi level of a n-doped semiconductor be below the one of a p-doped?

In a pn-junction, the difference in Fermi level between the p doped and the n doped regions causes the apparition of a built-in electric field at equilibrium. This electric field goes from the n to ...
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237 views

Calculation of RMS current in half wave rectifier

While calculating RMS current in half wave rectifier, why we will consider only half wave that means only we consider the limits 0 to pi. But here RMS current is for AC input..so why don't we consider ...
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BJT transistor as an amplifier [migrated]

I'm confused about a couple of things concerning the transistor.. is Vcc the signal to be amplified or Vin? And does the transistor actually amplify the voltage fed to it or does it just regulate how ...
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How long is the surface migration length of adatoms deposited by thermal evaporation in vacuum?

The deposition of metals through thermal evaporation involves the process of adatoms migrating on the substrate before its kinetic energy decreases to a certain point or before encountering a cluster. ...
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Why can't a reverse biased diode conduct by majority carrier injection (UPDATED)?

I know that the question "why can't a reverse biased diode conduct" has been asked before (here and here), but I'm asking it from a bit different perspective. Why can't we inject electrons into the ...
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825 views

Why is the law of the p-n junction valid under forward bias?

I'm currently studying the physics of the PN junction. I went though the derivation of the built-in potential in the PN junction under equilibrium: $$ {Diffusion\ current\ density} = {Drift\ current\ ...
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Question about electron-hole pair generation in depletion layer for a p-n junction photodiode

At the heart of operation of p-n (or p-i-n) junction photodiodes is the absorption of photons leading to generation of electron-hole pairs. If the diode is, e.g., reverse biased, then the motion of ...
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What is space charge Capacitance of diode?

Most of the books say that $p$-type and $n$-type materials of diode act as parallel plates of space charge capacitance were as the depletion charges (uncovered) act as dielectric. Then why do these ...
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How does the current flows through the collector-base junction of an NPN transistor operating in saturation? [migrated]

From what I understand, in the saturation mode of NPN transistor, both EB and CB junctions are forward biased. Now, if the voltage across CB causes it to be forward-biased, how does the current flow ...
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How does a minority carrier diffuse?

I have gone through a lot of questions but none of them ask how do the minority carriers approach the depletion layer in the first place. When a p-n junction is formed, negative space charge ...
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Difference between inorganic and organic semiconductors: electronic structure or configuration, or?

Organic semiconductors differ from inorganic semiconductors. In organic semiconductors the molecules are held together by weak van der Waals interactions and in inorganic semiconductors by covalent ...
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Electronics book for physics undergraduates

I am going through very hard time studying electronics, I studied little electronics at high school (what is diode, transistor, etc). Now in clg now I need electronics to study, I don't understand ...
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Hall effect with similar positive and negative carriers?

The Hall effect includes the transverse (to the flow of current) electric field set up by the charges which accumulate on the edges, to counter the magnetic component of the Lorentz force acting on ...
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730 views

What is a Dirac semimetal?

What is the precise definition of a Dirac semimetal? Is it sufficient for two bands to touch at a single k point with a linear crossing, or are more conditions required for a material to be called a ...
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How to estimate the heat generation and the power per square cm provided the resistance and the current of a laser diode?

Laser Diodes are very tiny. So, it is making me confused in its calculation. In laboratory, the resistance of a laser diode is 10-15 ohm and the current is 80-100 mA. How could I estimate the heat ...
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How to make a monocrystalline silicon seed

I do understand that you can grow monocrystalline silicon from an initial seed but I'm lost in a chicken versus egg situation where I don't understand how you can get the seed if the only way to make ...
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Working point of a transistor circuit [migrated]

I've stumbled upon this problem which involves a circuit with 2 transistors that are connected to each other. I'm trying to find a) the "working point" ($V_{ce}$, $V_{be}$, $I_c$, $I_b$) of each ...
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Is carrier charge density and carrier mobility constant in a given material?

If we assume the semi-conductor is doped by a variable amount, is there some way I can look up carrier charge density for the material in a reference somewhere? What about carrier mobility?
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What can justify the decrease of the electrical conductivity with the increase of light intensity?

I have currently been working with a sample that "appears to" decrease its resistance when I cover it and protect it from light. Basically it presents the opposite behaviour of a photoresistor. What ...
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How does one go about designing a substrate heater for PVD? I need to design one that can go till 1000 C in Oxygen.

Can I just use a Kanthal wire and make a pattern on a ceramic base? Wouldn't such an exposed element get shorted when I use substrates like Silicon? But wouldn't a layer of ceramic on top of the ...
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(If and) Why does cold temperature affect semiconductors?

I had a college student build an overclocked PC using phase-change technology. (This is essentially an air-conditioning unit with the evaporator attached directly to the motherboard.) He said that ...
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How can excite a semiconductor to make a photon just by heat in room temperature?

I want to know if a semiconductor in room temperature can excite by heat, producing photon, without any other source of energy?
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How is it guaranteed that electrical connections could be made without destroying a diode laser?

A diode laser is a tiny diode and requires a microscope to see it. Since a laser generates a good amount of heat, the diode should be destroyed with the produced heat. But it does not happen. but why ...
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Relation between interlayer tunneling amplitude and external potential in Bilayer graphene

What is the relation between interlayer tunneling amplitude ($\gamma_1$) and external potential applied ($U_{ext}$)? Is there any mathematical relation?
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What factors cause the velocity saturation to occur at different electric fields for different materials?

In semiconductors the velocity of carriers gets saturated after a certain value of electric field. In silicon it occurs at around $10^4 kV/cm$ and in GaAs at some other value. What factors are ...
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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 ...
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Why the bandgap of inorganic semiconductors decreases with temperature?

The temperature dependence of the energy bandgap in inorganic semiconductors is given by $$E_g (T) = E_{g,0} - \frac{\alpha T^2}{T+\beta}$$ where $\alpha, \beta$ are both positive, and the (somewhat ...
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what is the effect of temperature on the resistance of a photoconductor?

As we know, for a photo conductor resistance tends to decrease with increase in irradiance, but with greater irradiance comes greater temperature. Also we know, photo conductors are ...
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Semiconductor problem: how much Boron is required to establish a certain amount of charge carrier density

The problem description is as follows: Boron is used to dope 1 kg of germanium (Ge). How much boron (B) is required to establish a charge carrier density of 3.091 x 10^17 / cm^3. One mole of ...
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What happens after an electron and hole combine?

OK so I understand that an LED is a pn junction where when a forward bias is placed across the junction, the electric field causes the electrons to combine with the holes and release a photon through ...
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Why is $np$ always equal to $n_i^2$?

For you guys who studied semiconductor physics must be familiar with the equation: $$np=n_i^2$$ I can understand why this is true for the intrinsic case (the broken bonds would always provide ...
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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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Internal Resistor in a Diode

When we talk about the resistance of a diode (of the P and N region), is this resistance like the one inside an Electro-Motive Force or it acts like a normal resistor (external electric field exist)? ...
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BEEM and Doping of semiconductors

When using Ballistic electron emission microscopy(BEEM) to Image a metal/Semi-conductor interface would applying n-type doping aide or prevent a BEEM current to be detected as BEEM works on the ...
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Are insulators and conductors arbitrary categories?

I have seen charts showing the transition from insulator to semi-conductor is at $10^{-8}~\frac{\text{S}}{\text{cm}}$ and between semi-conductor and conductor is $10^{3}~\frac{\text{S}}{\text{cm}}$. ...
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Temperature dependence of the relaxation time in Boltzmann equation for impurity scattering in metals

Is there any temperature dependence of relaxation time in impurity scattering of conducting electrons? It seems to me that there is none. But, some people claim that there is. So if you could ...
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498 views

III-V semiconductor compounds - band gap approximations

I'm looking for the most common and accurate approximation functions for III-V semiconductor compounds. So far, I found two (InGaAs as the sample compound): The simplest one: ...
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Why do electron and hole mobilities decrease with temperature?

From page 35 of "Microelectronics" by Millman Grabel Mobility $\mu$ decreases with temperature because more carriers are present and these carriers are more energetic at higher temperatures. ...