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.

learn more… | top users | synonyms (2)

0
votes
0answers
104 views

Working of a phototransistor

Can anyone explain how photogenerated current in the base gets amplified in a phototransistor. If you use band energy diagram, then I would understand more quickly and clearly.
3
votes
1answer
136 views

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. ...
4
votes
3answers
290 views

How does temperature affect photovoltaics (PV) efficiency?

I know that photovoltaic panels are more efficient at lower temperatures: As the temperature increases, the output voltage decreases. I am looking for an explanation of the mechanism behind this ...
4
votes
2answers
321 views

Why isn't there a potential difference across a disconnected diode?

I know this question sounds silly, as if there was a potential difference a current would be created when the terminals are connected together and this would mean energy has come from somewhere. The ...
12
votes
1answer
490 views

What is the probability of quantum tunneling occurring in this CPU?

You may have noticed over the last few years that Moore's law is no longer applying to the real world. This observation states that over the history of computing hardware, the number of transistors on ...
6
votes
1answer
654 views

The skin effect and the reflectivity of gold

I am simulating a waveguide in COMSOL, a FEM solver. My model looks like this (it is similar to a standard Quantum Cascade Laser geometry): Therefore there is a very thin (30nm) layer of gold ...
1
vote
1answer
203 views

CCD's and the photoelectric effect

Do charge coupled devices as found in telescopes use the photoelectric effect if not what eles librates the electons. Also what is charge intergration in reation to CCD's.
1
vote
1answer
51 views

Is the valence band neutral?

While studying about band theory of semiconductors, I observed that when the electrons were excited from the valence band to the conduction band, they left behind holes in the valence band. From my ...
2
votes
1answer
387 views

Why does overclocking a CPU cause it to generate more heat?

It seems odd to me that overclocking a CPU causes it to consume more energy. The amount of energy flowing through the CPU should be related to the average number of 'gates' (or transistors) that ...
2
votes
1answer
859 views

PN Junction. Germanium VS Silicon

As far as I understood, when we connect P and N materials, electrons from N drift to P, thus create negative ions in P and positive ions in N. => electric field (barrier potential) must depend on an ...
1
vote
1answer
91 views

How big was the first transistor?

The first working point-contact transistor made in 1947 by Bell Labs. I'm looking for specific dimensions, all I've been able to find is "Fits in the palm of your hand".
1
vote
1answer
151 views

Why is titanium dioxide transparent for visible light but not for UV?

I wonder the reason for TiO2 thin films to be transparent for visible light but not for UV. I made a quick search and I found that it is due to the band gap of TiO2. It absorbs UV light but not ...
5
votes
0answers
41 views

Model for a thin metal/semiconductor junction?

Are there any books or articles that describe models for transport in a metal/semiconductor junction where the thickness of the semiconductor is less than the thickness of the depletion/accumulation ...
1
vote
1answer
167 views

n-p-n p-n-p and n-n-n heterostructure for LED

I was studying LED Heterostructures and I found out that my book is always giving reference to p-p-n type heterostructure. So I looked up into another book in order to find other type of ...
4
votes
1answer
839 views

What the heck is negative effective mass?

I am reading this book:Solid State Electronic Devices by Ben G Streetman and Sanjay Kumar Banerjee. I have some doubts in the article 3.2.2 Effective mass. In this the aythors say that ...
0
votes
2answers
241 views

List of experimental band gap

does anyone know where one can find a list, database, book of experimental bandgap values of semiconductors? Is there such a collection? Or do I need to scour papers one at a time to get the values?
1
vote
1answer
559 views

Band gaps: are they at the centre or at the edge of the Brillouin zone?

Reading about electronic band structures, I came across the following: Band gaps open at the edges of the Brillouin zone (BZ), since that is where the Bragg scattering occurs. I am slightly ...
1
vote
2answers
744 views

How depletion region is developed in a Schottky diode?

In a P-N junction depletion region is developed when electrons from N-region diffuse to P-region and hole from P-region diffuse to N-region. Here diffusion thereby development of depletion is caused ...
1
vote
2answers
65 views

Conductivity of a crystalline solid

In a crystalline solid each atomic level 'splits' into n levels (n = number of atoms in the system). When the number of atoms is large each level becomes replaced by a band of closely spaced levels. ...
0
votes
1answer
171 views

Light intensity (affected by semiconductor's absorption)

An experiment recently was done in order to measure the band gap of certain semiconductor. In order to gather the transmission coefficient for a spectrum of light, a light intensity of the system ...
4
votes
1answer
6k 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?
2
votes
0answers
274 views

Derivation of existence of energy band gap in semiconductor (solid State)

I am looking for both a mathematical and a physical reason for energy band gap in metals. For Physical reason, I was told that at each reciprocal lattice, you could have Bragg scattering, that would ...
1
vote
0answers
91 views

Basic concepts in quantum theory to start learning semiconductor physics [closed]

What basic concepts in quantum theory one must known to start learning semiconductor physics?
2
votes
1answer
125 views

What do I get when measuring on top of metal/insulator/metal by kelvin probe?

I am using a macroscopic Kelvin Probe for work function measurement. There's one confusing condition. If I measure a trilayer thin film stack with a structure of ITO(bottom)/PMMA(100-200nm)/Al(top), ...
1
vote
2answers
346 views

What are the differences between supperlattices and Multiple Quantum Wells Semiconductor Structures?

Semiconductor Optoelectronics: What are the differences between multiple Quantum Wells and supperlattices.
2
votes
1answer
448 views

What is the derivation of the formula for the probability of transmission through a barrier?

This site has a formula for the transmission probability over a barrier (in transistors): $$ T \propto \exp [-2(2m^*/\hbar ^2)^{1/2}(q\phi)^{1/2} d ]. $$ Where $T$ is the transmission probability ...
1
vote
0answers
48 views

Vacancy Generation / Annihilation Time (Relaxation Time)

Vacancy Generation/Annihilation Time, Recombination Time and Relaxation Time ($\tau$) are all synonymously used in atomic physics literatures. They're defined as the time that it takes for vacancies ...
2
votes
1answer
217 views

Effective mass of a particle

I was reading about concept of effective mass on Wikipedia and came across the line that effective mass of a particle can be negative and even zero. How is this possible?
1
vote
1answer
144 views

What is the speed of electrons in a transistor?

What is the average speed of an electron in a MOSFET transistor, and how can you calculate this? I've heard people throw terms such as "drift velocity" and "Fermi velocity" around, but I've never ...
1
vote
2answers
101 views

Rms value of rectified output from a half wave rectifier

The rms value of an alternating quantity which is the input to a half wave rectifier is $\frac{I_{max}}{\sqrt2}$. Then the rms value of output should be $\frac{I_{max}}{2} \sqrt 2$. But it is given ...
3
votes
2answers
96 views

Can zinc nitride be used as light emitting material?

I cannot manage to find any journal papers about the applicability of zinc nitride as active layer of an light emitting diode (LED). But certain papers got mention that zinc nitride with a direct ...
5
votes
2answers
692 views

Why absence of electron is called hole?

I am having hard time in understanding the concept of holes: If there is no electron than how can it be a hole? For a moment lets assume absence of electron is termed as hole but how can this absent ...
1
vote
2answers
2k views

Silicon atom: How is it replaced by a Phosphorous (or Boron) atom?

My book says: A pure semiconductor at room temperature possesses free electrons and holes but their number is so small that conductivity offered by the pure semiconductor cannot be made of ...
0
votes
0answers
1k views

The Gunn diode and the two valley theory

In today lecture of microwave and radar my teacher explained about the Gunn diode. He said it is made up of only one type of matrial e.g. $GaAS$ as shown in (a) part of the image. He said that there ...
0
votes
0answers
79 views

Confusion in biasing a NPN transistor in CE config

In CE configuration of NPN transistor, collector emitter junction is reverse biased. But how is a N-N junction reverse biased?
1
vote
1answer
89 views

Diodes (Forward biased)

Why does the width of the depletion region decrease,when the diode is forward biased?Is it because the ions have moved to p-junction,or n-junction? Please clarify.
2
votes
1answer
527 views

Why doesn't current flows in reverse biased diode?

Consider this reverse biased diode : I read that no or very small current flows in reverse biased diode as depletion layers get widened and huge resistance is offered so no electrons can cross it. ...
0
votes
1answer
254 views

Charge density in depletion layer for pn-junction

I just came across this Wikipedia article on pn-junctions: pn junction What I don't get is why the negative charge density is narrower/smaller than the positive one in Figure A. I'm guessing the ...
1
vote
0answers
60 views

How does a liquid crystal on Silicon affect the phase of incident light?

When a polarized light beam is directed to a phase-only LCoS system how is the phase modulated ? What is the physical effect behind ? Does voltage modulation has an impact on birefringence ?
4
votes
1answer
229 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 ...
2
votes
1answer
142 views

Why is more intrinsic carriers bad for high temperature semiconductors?

I'm taking a solid state course, and is currently on the subject of dielectrics. In one of the sections, concerning "Impurities in Dielectrics" the books says: "Impurities can also be used to make ...
0
votes
2answers
414 views

What actually happens at the microscopic level in a Zener diode in reverse bias?

A Zener diode is used as a voltage stabilizer. The graph of current vs voltage of Zener diode clearly shows that there is a constant voltage across Zener after the breakdown voltage as the current ...
2
votes
0answers
98 views

Fermi Energy and the Electric Potential

In an extrinsic semiconductor the electric potential is: $$\phi = \frac{1}{q}(E_{\mathrm{F}} - E_{\mathrm{Fi}})$$ where $E_{\mathrm{F}}$ is the Fermi energy, $E_{\mathrm{Fi}}$ is the intrinsic Fermi ...
1
vote
1answer
11k views

Dielectric Constant or Permittivity of Metals

I'm wondering what the dielectric constant or permittivity of metals is --particularly copper. Do metals have an infinite permittivity?
1
vote
1answer
212 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 ...
1
vote
1answer
1k 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 ...
1
vote
1answer
114 views

Conductive glue

I would like to use some conductive glue to contact a silicon chip's back gate. Any suggestions on what to use? Can I use thermal silver paste? I would be operating at cryogenic temperatures below 4K. ...
1
vote
0answers
93 views

Nature of electron states in a semiconductor

Usually one is led to think of an electron moving from the valence band to the conduction band as an electron leaving the atom it is bound to in the lattice, and becoming free to move, while leaving ...
0
votes
2answers
501 views

Understanding Wikipedia's “Semiconductor Band Structure” diagram where the bandgap appears to increase with increasing density of states

I'm having a bit of trouble understanding the semiconductor band gap diagram on Wikipedia: (from Band gap article). Why is the size of the band gap increasing with the Density of States (DOS) in the ...
5
votes
4answers
1k views

Why do solar cells have a window layer on top of the absorber layer and not below it?

In solar cells there is a p-n junction. P-type semiconductor (for example CdTe) is often absorber layer because of its carrier lifetime and mobilities. In case of CdS/CdTe,* CdS is n-type window layer ...