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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What is the wavefront quality of VCSELs? How does the wavefront quality of VCSELs compare to Fabry-Perot laser diodes and DPSS lasers?

I am currently looking at this VCSEL. According to the datasheet, it has a narrow spectral linewidth and emits a Gaussian beam, which are both properties that I find interesting. But I'm also ...
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What is fundamental band gap?

This is purely a terminology question. Let us suppose, we are looking at a semiconductor. I understand what is the difference between direct and indirect band gap. However, in some papers I came ...
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Holes in semiconductor

Why do we introduce the concept of holes in semiconductor physics? Why don't we just describe hole current as of the current due to the electrons in the valence band. is the concept of holes necessary?...
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Solving junction barrier voltage [closed]

If two or three temperatures are given in the question, should I find all their voltages or just one?
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Electric field in diode

I read that the electric field in a diode aids the flow of minority carriers (drift current). However, why is the eletric field direction simply represented with a single arrow? Shouldn't it look like ...
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43 views

Parabolic band structures $k$-point distribution [closed]

In the parabolic band structure approximation for semiconductors we can consider a direct band gap where the conduction band (CB) and valence band (VB) are given as $$ E(\vec{k})_{cb} = E_c + \frac{\...
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How does the Fermi level of different materials reach equilibrium when in contact?

I'm a college student studying semiconductors. I can't understand what is happening inside the materials when two or more different materials are in contact. Can I get some help? So, basically at ...
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How are dies, diodes, chips and the like separated from each other on a wafer? [closed]

I would like to know how the single dies on a wafer are (electrically) separated from each other. Are they even? More precisely, as the wafer themselves are held on a so-called susceptor (basically ...
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1answer
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P-N Junction Diode (Semiconductor)

I have read that in a p-n junction, free electrons from n side diffuse to the p side and then recombine with the holes of p side. Here, it does not refer regarding energy bands. However, free ...
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Stacking peltiers

I want to build peltier based cloud chamber thus I need to cool a thin plate so Qload would be small. I need help to better understand how stacking of peltiers works to achieve the lowest temperature ...
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1answer
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How does a coherent state excite charge carriers across a semiconductor band gap?

In standard semiconductor theory, we have a valence and conduction band energetically separated by band gap energy $E_g$. A photon with energy $E>E_g$ can excite an electron-hole pair from the ...
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Is semiconductor theory really based on quantum mechanics?

Often semiconductors are cited as the big application of quantum mechanics (QM), but when looking back at my device physics book basically no quantum mechanics is used. The concept of a quantum well ...
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What dictates the efficiency of a semiconductor?

Semiconductors can be used for a heat exchange but are less efficient than a Freon air-conditioning system. What dictates this efficiency?
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How can quantum dots beat shockley-queisser limit? (Particularly PbSe/S)

What is the main reason that we use QDs for solar cells? As the title says I am more interested in PbSe or PbS. To my thinking, the reason for using QDs is that creating quantum confinement effects ...
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Difference between orbital Rashba effect (ORE) and orbital Hall effect (OHE)

What is the difference between the orbital Rashba effect and the orbital Hall effect? I am very confused with these two effects regarding the literature. References: Orbital Rashba effect: D. Go et ...
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Semiconducting properties of diamond imperfect crystals

Suppose we want to make a diamond crystal and during the process point defects(lattice gaps) are created. Which is the energy of the electrons?(red circles)Can we deliberately create those point ...
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1answer
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Pressure dependence of electric conductivity of solid semiconductors

For semiconductors, if we increase the temperature, the band gap of a solid is reduced and more electron-hole pairs are generated -> greater motion of charge carriers in the bands -> greater ...
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How Does Semiconductor Vacuum Energy Change with Doping?

In the paper "The application of semiconductors with negative electron affinity surfaces to electron emission devices" negative electron affinity is defined by the condition ($E_c - E_f) >...
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1answer
79 views

Current contribution in a p–n diode under equilibrium

We say that under equilibrium, no further movement of majority carriers takes place due to the immobile ions or the electric field or built in potential stops it. But in many cases and videos I seen, ...
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Shifting of Energy levels in PN junction under Equilibrium

My question is during equilibrium is achieved under no biasing, why it is that in fermi level diagram representation fermi levels are raised in p type nd lowered in n type. Is it not possible we ...
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Nearly free electron model: How to diagonalize the perturbation Hamiltonian?

In the Nearly free electron model, we treat a weak periodic potential as a perturbation to the free electron model so $$H_{tot}=H_0+V(\vec{r})$$ where $H_0=\frac{\hat{p}^2}{2m}$ and $V(\vec{r})=V(\vec{...
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1answer
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Diffusion and Drift Current under no biasing of a PN junction Diode

In a PN diode, I get the point that total current is zero due to drift and diffusion current contribution cancels their effect when depletion region is formed. My question is even though just for a ...
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1answer
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Would a macroscopic sphere with the thicknesss of a few atoms behave as an artificial atom?

As quantum dots are composed of closely packed atoms, where their electronic levels are bound and in a confined system, would a similar system, with the same thickness as a quantum dot but much larger ...
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1answer
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Nearly free electron model and perturbation theory: How to determine matrix elements of perturbation?

In Steven Simons The oxford Sold state basics, the Nearly free electron model is tackled by treated the weak periodic potential as a perturbation to the free electron model. That is, the full ...
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Why is the effective mass of silicon anisotropic?

The effective mass is a tensor property of rank two. It may be anisotropic if the corresponding electron band is not perfectly isotropic. For silicon, this seems to be the case. However, there exists ...
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1answer
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What makes of a current in solidstate/semiconductor physics?

If there is some incoming light that has hit electrons of a N-type doped silicon and broke loose these electrons from their covalent bounds and excited them to the conduction band and also excited the ...
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Why are polycrystalline solar cells shinier than monocrystalline solar cells?

Being shiny reduces the efficiency of the solar cells. Additional to the grain boundaries that polycrystalline solar cells have that gives resistance to the current flowing in them, they are shinier ...
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Confusion about ionised atom, free electron, conduction band, donor energy level and acceptor energy level

I have some confusion about the concept of some electronic bands and energy levels. Beyond valance band, For an atom, can having at least one electron in the conduction band mean that the atom has ...
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Is it possible for the voltage drop across the depletion region in a diode to be more than the actual biasing voltage?

We know that there will always be a net current in the circuit between the two terminals of the forward biasing voltage source, however small the forward biasing voltage is (see @jonk 's comment). ...
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Is silicon a semiconductor or insulator?

I have read that pure crystalline silicon is an insulator because it has a such covalent bond that very tight and no free electrons available for conduction bands. They all are bonded with other ...
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Is the dynamic resistance of a diode due to the narrowing and widening of the depletion zone?

All diodes have a built-in voltage. When a diode is connected under forward or reverse bias, the depletion region either widens or narrows. Obviously, the barrier height also increases or decreases ...
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Laser diode tests - voltage sweep vs current sweep. What's the difference?

I can't wrap my head around it. There's no current without voltage (except eddy currents), and there's no voltage if there's no current, when you pass the current through a diode. So why do people ...
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79 views

Dynamic resistance of diodes and the depletion zone

According to Resnick, Walker & Halliday's Fundamentals of Physics (10th edition), Figure 41-15 shows why a p-n junction operates as a junction rectifier. In Fig. 41-15a, a battery is connected ...
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Understanding minority charge injection

Due to the applied voltage, electrons from n-side cross the depletion region and reach p-side (where they are minority carries). Similarly, holes from p-side cross the junction and reach the n-side (...
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How does 3s, 3p energy levels of Si in vicinity of other atoms interact to give four new orbitals?

I was studying about semiconductors in Kasap S.O book - "Principle of electronics". This statement "3s, 3p energy levels of Si in vicinity of other atoms interact to give four new ...
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1answer
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Which lamp(s) will glow? [closed]

I thought it would be through lamp 1 and 3 because the electrons can go through the circuit between lamp 2 and 3, then through lamp 3 then through the circuit between 2 and 3 again and finally down to ...
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Absorption spectral broadening of molecules in solution compared to films

During an experiment we measured the absorption spectra of a compound in solution and also made a measurement for the same compound in solid film. Usually when I done this for other compounds there ...
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How does a transistor work?

Here we can see a Bipolar Junction Transistor (BJT), which has a common base configuration. My instructor recently explained to me its working principle, but I didn't understand his explanation ...
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Unbiased PN junction Diode

I have certain doubts regarding the formation and movement of majority charge carriers when a p type and n type semiconductors are fused together. When electrons and holes mover from p to n and n to ...
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2answers
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In LED's do the number of charge carriers (electrons and holes) decrease with time?

According to page-1268-69 of Halliday, Walker & Resnick's Fundamentals of Physics (10th edition), To emit enough light to be useful as an LED, the material must have a suitably large number of ...
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1answer
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In semiconductors, do free electrons and holes ever mix to become neutral?

According to page-1262 of Fundamentals of Physics by Halliday, Resnick & Walker (10th edition), Both the electrons in the conduction band and the holes in the valence band serve as charge ...
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Semiconductor law of mass action

When studying semiconductors, one would surely encounter the law of mass action for semiconductors: $n \cdot p = n_i^2$ And I've found a variety of different explanations for it, but none was actually ...
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1answer
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Will the depletion layer of a p-n junction stay extended after being disconnected from the circuit where it was connected under reverse bias?

We know that the depletion layer/region becomes longer when a diode is connected under reverse bias in a circuit (Is my grammar correct?). Now, my question is, if we then disconnect the diode from the ...
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1answer
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Why and how is hole trapping happens by acceptor impurities only and not by donor impurities of a semiconductor detector?

Why and how is hole trapping happens by acceptor impurities only and not by donor impurities of a semiconductor detector? Am I missing very basic phenomena?
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At absolute zero, how does the gap between the valence band and conduction band increase in silicon crystal?

My book states, " At absolute zero temperature, the electrons are tightly bound by the atoms. At this temperature, the covalent bonds between silicon atoms remain very strong and all the valence ...
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1answer
152 views

Thermal averages with opposite sign in the exponential

I've recently seen an example where a thermal average was carried using a plus sign instead of the usual minus sign inside the exponential. $$\langle \mu \rangle = \frac{1}{Z} tr(e^{\beta H }\mu) \...
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Is generating electricity from triboluminescence feasible?

I read an article about triboluminescence where sticky tape under a vacuum produces x-rays as it's peeled away. I was left wondering if the generated x-rays can be converted into electricity using ...
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Is there a difference between $\rm SiO_2/Si$ and $\rm Si/SiO_2$ when describing the substrate of a field-effect transistors?

I've seen in different papers that the substrate of a FET is SiO2/Si or Si/SiO2 are they describing the same thing or is the order important?
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Why are electrons usually used to define qubit in silicon-based quantum dot, but not holes?

Usually, electrons spin are used to define qubit in sillicon. In contrast, holes are usually used in description of germanium qubit. Why is that?
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Why electrons are freely moving in valence band? If they are moving why not any current? [closed]

Why electrons are freely moving in valence band? If they are moving why it does not have any current? For all the cases?

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