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 affect it.

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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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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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Diffusion and Drift currents in a PN junction

In a forward-biased PN junction, the potential barrier decreases, allowing more majority carriers from one side to diffuse to the other side where they are minority carriers. After they cross the ...
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864 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 ...
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19 views

Tunnel diode/quantum tunneling

How does a tunnel diode work?/How does a tunnel diode use quantum tunneling, and how does quantum tunneling make the diode faster?
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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 ...
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184 views

In a positively biased PN junction, where do the injection carriers come from?

I am not quite understand i-v character of PN-junction diode. Here is the model in textbook. The PN junction diode can be divided into three regions. They are One depletion region near the PN ...
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74 views

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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123 views

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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80 views

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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5k views

Difference between steady state and equilibrium?

In semiconductor physics, what is the difference between steady state and equilibrium. How analysis of devices varies in these processes?
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Kirchoff's voltage law doesn't seem to hold in an experiment conducted with series resistor, diode and signal generator

I've conducted an experiment to look at the electronic characteristics of a diode. This was done using a series diode, resistor ($R$) and signal generator. The signal generator was made to supply a ...
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Shining light (of a particular frequency) on an insulator to make it into a conductor

Recently I read about band theory of solids. The energy difference between valence band and conduction band determines the conductive property of solids. Suppose I take an insulator and shine it with ...
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266 views

If we connect a block of p-type semiconductor only to a positive terminal, will it become positively charged?

Connect the positive terminal of a battery to a piece of p-doped semiconductor, say, silicon doped with boron. Will the terminal pull electrons out of the doped silicon, or equivalently, inject holes ...
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Do batteries provide electrons

In chemistry, the reaction at negative electrode produces electrons,which flow to the positive electrode through the circuit. But then, if circuit has a conductor, then wouldn't it also release ...
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3D device simulation of diode (static) [migrated]

I am looking for a simple 3d software solving the drift and diffusion model for a diode in equilibrium. (Very simple abrupt p/n-junction - even without contacts. Purpose: teaching). I know Silvaco ...
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22 views

Optics - Photodiodes - minimum photon energy that a photodiode will be sensitive to [closed]

I'm foraying into the world of photodiodes, and I'm trying to calculate the minimum photon energy required for the photodiode to be sensitive to. Symbolic expressions desired. Minimum detectable ...
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30 views

Does the Fermi level change under change of temperature, voltage or other conditions?

From a previous post with similar title, (What's the difference between Fermi Energy and Fermi Level?) I think it is safe to assume that In a block of material, Fermi energy is the level, up to ...
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2k views

How does temperature affect a semiconductor band gap?

From this link, I've read that An increased interatomic spacing decreases the potential seen by the electrons in the material, which in turn reduces the size of the energy bandgap. Can this ...
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34 views

Why is a substrate needed in growing GaN?

Is the substrate a layer on which GaN crystal grows on? Is there a way to grow free-standing GaN? Would the resultant crystal be full of defects?
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70 views

Does doping silicon affect its coefficient of thermal expansion (CTE)?

Everywhere I have searched I always see the CTE of silicon listed as 2.6*10e-6 °C^-1. However, I have silicon that was phosphorus-doped to an ion concentration of of 2.41*10e11 atmos/cm^3, and I would ...
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When a pn junction is formed, why is a positive region of charge formed on the n side of the junction?

I understand that when electrons diffuse from n-side to p-side, negative charge is developed on the p-side. But the mere absence of electrons on the n-side doesn't make that positively charged. The ...
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62 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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What is the dependance of voltages in a MOSFET on its Performance? [migrated]

The Wikipedia page says that (in context of scaling) To maintain performance, the threshold voltage (Vth) of the MOSFET has to be reduced as well. And also, this paper says, For high ...
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159 views

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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43 views

What is the relationship between Raman peaks and phonon vibration modes?

I've seen Raman spectra, such as here, where peaks at certain wavenumbers were identified with phonon vibration modes (TO, LO, TA, LA). What is the relationship behind this, and how could I make such ...
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405 views

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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Flaw in Einstein's explanation of the photoelectric effect?

The essence of Einstein's idea is like this: if a system is in some bound state with energy $-E_b$ with $E_b> 0$ (the threshold of the continuum band is taken as zero), and we drive the system ...
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31 views

The meaning of the temperature in the Shockley Equation

In the Shockley equation, which is the model of the $I$-$V$ curve of a p-n junction, what does the Temperature refer to, carrier temperature or lattice temperature? When a p-n junction subjected on a ...
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Relation between carrier temperature and lattice temperature, under injections

When we are learning the semiconductor physics, we always encounter a key concept, which is the carrier temperature. However, there is not any detailed definition of such carrier temperature. Do we ...
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314 views

Donors/Acceptors in Metal Oxides

Can anyone explain to me why most articles describe chromium as an acceptor in titanium dioxide? In TiO2, titanium has the charge state Ti$^{4+}$ and oxygen has the charge state O$^{2-}$. When Cr ...
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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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107 views

Optical mode leakage through a layer of gold

The geometry of my semiconductor device is given below. The blue regions are gold, the grey ones - gallium arsenide (n-doped to $2.9 \times 10^{15} \mathrm{cm^{-3}}$). The dimensions are μm, i.e. it ...
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Do electrons in the conduction band have a quantum number?

Sorry if this is a silly question, but I haven't seen the concept anywhere and was wondering why. If valence electrons can have a quantum number, why can't conduction electrons? Is there something ...
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170 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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96 views

Does Saturation velocity in semiconductors have a relation with the wavelength in which the peak in the absorption spectrum occurs?

Saturation velocity is the maximum velocity a charge carrier in a semiconductor, generally an electron, attains in the presence of very high electric fields. (source) I want to know if the ...
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5answers
3k views

How can doped semiconductor be neutral?

I have studied about the two types of doping which result in p and n type semiconductors. I also came to know that they are neutral. But, how can it be? Is it that the positive charge(holes) in ...
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Numerical Solution of 1D Boltzmann Transport Equation

I need to solve the one-dimensional Boltzmann transport equation in a semiconductor numerically, and I want to take a deterministic approach toward the problem (i.e. not use Monte-Carlo or similar ...
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Why do the free electrons in N-type want to diffuse?

I'm trying to understand how a diode works and for this I've used(among other resources) the book written by Albert Malvino, Electronic Principles. Everywhere I read about this topic, it says that ...
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31 views

Activation energy as a function of defects

Electrical conductivity has a form of Arrhenius equation. It is assumed that activation energy decreases with defect density in the insulating state and becomes zero in the conducting state. Can one ...
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Factors on which barrier potential in a p n junction depends

I have a few queries regarding the barrier potential in a p-n junction diode. Is the barrier potential dependent on temperature? Why/why not? Does the barrier potential depend on doping ...
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65 views

How holes conduct current?

I had questions about holes in semiconductor, when i checked the net it is said holes are said to be equivalent positive charge and they say because the hole moves from one place to another when it is ...
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What controls the on-off speed in a microprocessor? [closed]

I've been spending some time reading about semiconductors and even about computer architecture in order to understand how computers actually works in lowest levels, but until now nothing what I read ...
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34 views

Complex dielectric constant in ultraviolet range

Dielectric constant of a material could be a complex number, which is dependent of the frequency of electromagnetic wave. From the Springer material website, I learn that both the real part and ...
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147 views

why activation energy of semiconductor changes as temperature changes

why activation energy of semiconductor thin films changes as temperature changes. I know that this is due to different conduction mechanisms. Intrinsic conduction mechanism which occurs at high ...
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10 views

How does the saturation current of a heterojunction depend on on the band gap difference?

In my textbook, they demonstrate that, for a regular n-Si/p-Si pn junction, the electron saturation current density (it's pretty much the same for the holes, but with hole properties instead of ...
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28 views

Why does the minority carrier drift current at PN junction remain constant when reverse biased?

I understand the source of this drift current is thermally excited electron hole pair minority carriers, and that minority carrier excitation is constant (and quite low) at constant temperature. ...
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20 views

Resistance of depletion region of PN Junction

It seems that in picture D, the Depletion region is gone because quantitatively we have V= Vj+RI where Vj is the opposite of the built in potential of the depletion region but R is the resistance of ...
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763 views

Explanation for transistor as amplifier

In transistor as an amplifier, we have NPN transistor (base in the middle and emitter and collector at the sides). The collector has electrons in majority because it is N-type. similarly, holes are in ...
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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 ...