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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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How does an op amp compare voltage? [migrated]

How does an op-amp know where the ground is because the inputs are single wires, how does an op-amp compare them to a ground like this circuit for example clearly the op-amp is not connected to ...
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Drawing input output equivalent circuit in feedback amplifier

In Millman and Halkias' "Integrated Circuits", while analysing an amplifier circuit, after identitying topology the second step is drawing equivalent input and output circuit. This step involves ...
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how to prove that the thermal activation of intrinsic carrier density is half the band gap energy?

I know that for an intrinsic case $E_a = 0.5E_g$ at $T = 0\text{K}$, I searched a couple of text books but I cannot relate between the band gap energy, the fermi energy from a side and activation ...
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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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Semiconductor and Photonic nano devices

Which structure and model we prefer to construct semiconductor and photonic nano devices and why? (a) Preodic Multiple quantum wells structure (b) Aperiodic Multiple quantum wells structure (c) ...
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21 views

Diffusion coefficient for electrons and holes in a semiconductor

I am trying to calculate the diffusion coefficient for electrons and holes in excess of each side of the junction p-n outside the depletion region. Silicon was used with electron mobility at 300 K, $\...
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Dark Current and Shunt Current temperature dependency contribution in photoconductive mode photodiode

There seems to be quite not much information online about the actual contribution factor of the temperature dependency of a photodiode in photoconductive mode. It is said that "In photoconductive ...
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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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48 views

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 ...
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Can nitrogen be used as a dopant in n-type semiconductors? [duplicate]

The heavier group 5 elements, phosphorus, arsenic, etc, can be used as dopants to produce n-type semiconductors. Why isn't nitrogen used as a dopant in n-type semiconductors?
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Is the band theory valid for an electron with energy greater than the potential?

Consider Kroenig Penney model. Here there is a derivation that uses the following potential: One of the assumption is that the energy of the electron is $E<U_0$. Under this assumption (and others) ...
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Why there's a voltage drop across a diode after its depletion is no more?

I have a question that's bugging me for a while. In a resistor, the thing dissipates energy and therefore drops voltage due to collisions. In a diode I understand that there's depletion region that ...
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Need help understanding an electronic oscillator (Schmitt trigger + capacitor) [migrated]

When we use this circuit, the LED blinks. I know an inverter transforms high to low voltage and low to high voltage. I don't understand how it does the latter and would greatly appreciate an ...
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Why are the electrodes in thermodynamic equilibrium for a working solar cell?

I was reading a paper that performed simulation of a solar cell under illuminated conditions. Obviously, in these conditions, the device is out of thermodynamic equilibrium. For example the ...
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Why the product of hole and free electron density is constant in semiconductor?

I have learned from a text book of electronics that the free electron density, n (which is equal to that of hole, p) of intrinsic semiconductor due to thermal excitation is a function of temperature ...
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1answer
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How can I calculate the chemical potential and the effective masses in an intrinsic semiconductor?

I want to calculate the chemical potential and the effective masses of the germanium charge carriers considering that the relaxation time is the same for the two carriers: electrons and holes. ...
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what is the ionization rate?

I'm wondering about the term "ionization rate". Especially in respect to silicon/semi conductors and electrons & holes. I do not understand why there is a difference between electrons & holes. ...
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Semi-conductor physics - Finding current when applied voltage is big

In this problem, I am given the original expression of the current when the applied voltage is low enough. Now I assume that must mean it's in a weak injection state. Afterwards, I am asked to find ...
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Why is silicon used for making solar cells?

Silicon has a bandgap of 1.1 eV, whereas germanium has 0.65 eV. Silicon has an indirect bandgap, whereas gallium arsenide has a direct bandgap. Still silicon is mainly used for making solar cells. Why?...
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Gauss's Law about excess charge on conductors, quantum mechanics, and doped semi-conductors [closed]

Does quantum mechanics predict that there is any probability of finding excess charge inside a conductor? I've read an explanation about the distribution of excess charge placed on conductors. The ...
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Change the depletion width in the presence of light in a photodiode

In my simulations, in the presence of light, the depletion width of the layer decreases. Can light change the depletion width of the photodiode?
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How to find the degree of doping in a material?

I find this term a bit mysterious, it appears that everyone is using it intuitively without proper definition (or at least I failed to find one). So the Physics Glossary defines it as In condensed ...
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1answer
33 views

In HPGe detector how electron-hole pair remembers energy information of incident gamma?

In the HPGe detector, any gamma energy (> e-h pair production E) shall excite the electron of the valence band and send it to the conduction band. Due to reverse bias, the conduction band e shall be ...
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What does ground in low voltage electronic circuits mean?

I have been confused a lot by the word "Ground". The ground that I've usually heard about is connecting a wire of appliances with the rod buried under earth but what does the word Ground mean when it ...
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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
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How do electron holes have spin, and how do they interact with “real” particles / vice versa?

So, I thought I had an uneasy truce with quantum mechanics but I read something today which made spotted combat flare up in my mind again. In solid state semiconductor free electrons certainly have ...
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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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Vanishing of Coulomb blockade/charge dispersion in high transparency Josephson junctions

I was recently reading the paper Coulomb Blockade in Superconducting Quantum Point Contacts by Averin from 1999 (see here for the ArXiV, here for the PRL). In here he discusses a peculiar phenomenon:...
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Richardson-Dushman Equation using Momentum Space

How can we derive the Richard Dushman Equation using momentum space? J=B$_0$T$^2$e$^{-(\phi/kT)}$, B$_0$=4$\pi$qmk$^2$/h$^3$ Am$^{-2}$K$^{-2}$, T=Temperature in Kelvin, $\phi$ is work function of ...
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Velocity normal to surface in thermionic emission

In the derivation of the Richard-Dushman law which relates the current density $J$ from thermionic emission in a filament of temperature $T$ and work function $\phi$ $$J = AT^2e^{-\frac{\phi}{kT}}$$ ...
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Bjt configuration

In common base configuration,we know that alpha is almost 1 which means that the base current is almost zero.But what is the physics behind this base current almost equal to 0?And similarly in common ...
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38 views

Semiconductor Quantum Dots

Can someone recommend some good books on semiconductor quantum dots(InGaAs, GaAs etc..) from the perspective of a beginner student. I mostly want to learn about the optical states(the ...
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How relate doping concentration and electron concentration?

Say I have Si with the donar doping concentration $N_D=10^{14} \text{cm}^{-3}$ and a temperature $T$. How can I relate the donar doping concentration to the electron concentration? I know the ...
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1answer
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Is diamond able to conduct electricity given 5.5 eV of energy? How do we then identify insulators and semiconductors?

I have learnt that the band gap for diamond, an insulator, is $5.5\:\rm eV$. Does this mean that diamond is able to conduct electricity if we give it this immense amount of energy (let's assume we do ...
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Fermi Level and Built -in potential of semicoductor

How can built in potential barrier of semiconductor be determined as the difference between fermi level in p- and n- side region ?
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1answer
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Doubt with another form of Balmer' Series

In the book I'm studying from (Solid state electronic devices - Ben Streetman) it is said that the Balmer series is defined as follows: $$ v = cR \left( \frac{1}{2^2} - \frac{1}{n^2}\right) $$ with c ...
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1answer
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LED diode: How are photons produced in the LED diode?

According to "Introductory semiconductor physics" by Greg Parker (1994; Amazon.com), a photon is produced when an electron recombines with a hole across the energy gap of a direct band-gap ...
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How can depletion region be formed at the center?

Let's consider an electron at the junction in the n-type region. As it moves into the p-type we say it leaves behind a positive ion and hence in this way electrons at the junction in the n-type create ...
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Existence of conduction electrons in pure Si at room temperature

Silicon has a bandgap of ~1.1 eV whereas the room temperature thermal energy is ~0.04 eV. But we still find electrons in the conduction band for a pure silicon wafer, away from any radiation. I ...
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activation of donors via annealing

I've been reading up on semiconductors and quantum computing in general and have come across "activating donors via annealing" a lot, in papers such as here for example. From what I gathered, they ...
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1answer
55 views

Who controls completing the circuit in a transistor? [closed]

Consider an npn junction. The p-type semiconductor p has holes which are filled by electrons provided either by the n-type or by phosphorous dopants. The transfer of charge from n to p forms a ...
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Mental contradiction: Valence electrons do not move at the non-zero wavevector?

I have a mental contradiction. Let's consider the following band structure with the Fermi energy somewhere inside the gap: where $\Gamma$ point represents the zero value of the wavevector $|\vec{k}|$....
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Substitution of $-E_F-E_g$ for $E_F$ in distribution function and transport integrals for holes

As far as I understand, holes occupancy governed through distribution defined as follows, $h=1−f=1−\frac{1}{e^{\frac{E-E_F}{k_BT}}+1}$ but when I tried to calculate transport coefficient involving ...
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2answers
70 views

Dark current and thermal excitation in CCDs

In charge-coupled devices (CCDs), doped semiconductors are used to produce an electronic signal from incoming photons - the underlying principle being the photoelectric effect. This simple law tells ...
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1answer
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Why is it not possible to dope semiconductors with elements with 6 or 2 valence electrons?

As far as I have learnt, semiconductors are often made using elements from the 4th group, and their properties are often enhanced by doping with either pentavalent or trivalent elements. Take the ...
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What is charge relaxation and spin relaxation in an atom/ artificial atom?

I want to understand the difference between these two terms.