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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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65 views

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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48 views

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
81 views

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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1answer
363 views

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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2answers
102 views

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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1answer
56 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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1answer
58 views

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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2answers
96 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
428 views

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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21 views

By shortening the N-type side to the P-type side of a diode with a wire, how does the electric potential looks like in each point of this circuit?

To avoid misunderstanding I'll first start with the notions. The electrochemical potential (which in semiconductors refers to as the Fermi level) is the sum of the chemical potential and electrical ...
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159 views

Is Fermi Level a property of the material?

I have gotten myself confused about the band structure explanation of semi-conductors vs insulators. The Wikipedia picture and the explanation surrounding it seem to suggest that Fermi Level is a ...
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0answers
181 views

What the difference between pin and pn diodes i-v curve?

For my understanding there should be no big difference in i-v curve between regular p-n junction and p-i-n junction, the only difference i can think about is do to the bigger resistance of the ...
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205 views

What is the physical interpretation of energy band graph in semiconductors?

Does this graph represent energy states in a single atom which makes it into the semiconductor or is this a representation of sum total of energy levels occupied by different electrons in the lattice ...
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29 views

Built In voltage drop across a pnn+ device

Will the net built-in potential of an p+,n,n+ device having two junctions(1.) that of p+ and n and 2.) that of n and n+ simply be the addition of the built in potentials of the junctions?
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48 views

Meaning of F(E)Z(E) in semiconductor theory

I really don't understand the following term $$ \int F(E)Z(E)dE$$ where $F(E)$ is the Fermi-Dirac distribution (but it could be any distribution) and $Z(E)$ is the density of states. What I really ...
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1answer
346 views

Confusion regarding Hall effect in semiconductors

In many places, it's mentioned that in hall effect, the holes move under the influence of magnetic field in the direction as shown in the figure. In this figure itself, the bound electrons move in the ...
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73 views

How does a hole do impact ionization?

Impact ionization is said to be generation of electron-hole pairs with help of free electrons and holes. I have the intuition on how a free electron would be able to generate electron hole pair. I can'...
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1answer
38 views

reverse / dark / leakage current

what is the difference between reverse, dark and leakage current of a (photo-)diode? From my current understanding it all seems to be the same?
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SiO2 layer in diodes

Can somebody please explain the purpose of this SiO2-layer? Thank you!
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161 views

Link between tunneling rate and conductivity

Generally speaking, in the theory of single-electron tunneling events (one electron tunneling through a quantum well), the rate under which this event occurs is calculated using Fermi's Golden Rule, ...
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54 views

Doping in semiconductors - location of new states

A short question relative to doping semiconductors: What defines the location of new energy states? For example, why does doping of n-type add energy states slightly below the conduction band (and not ...
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91 views

is semiconductor in thermal equilibrium?

If a semiconductor is heated such that there is no temperature gradient, is it under thermal equilibrium? I have studied that if no temperature gradient exists across a semiconductor then it's in ...
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11 views

Impurities in HPGe crystals

Is there any way that one can find the impurities existing in an HPGe crystal? This is required for making an accurate simulation of the material of the crystal including the concentrations of Ge and ...
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2answers
2k views

Is Fermi level located above or below donor levels in n-type semiconductor?

I find contradicting information about this. Some resources says it's above donor levels Hyperphysics website: and other say it's below, eg. on this ResearchGate thread: in n-type semiconductor,...
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160 views

Change of refractive index using semiconductor

I was wondering, if it is possible to change the refractive index of a semiconductor using an electric field or current? I have heard about injecting charges to tune the refractive index. How/Why does ...
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1answer
36 views

Change Carrier Density Of Semiconductor [closed]

Do you know how you can actively modulate the carrier density in a semiconductor ?
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375 views

How does base-emitter voltage affect the current gain of a transistor?

I'm doing a Physics project related to transistor operation. My data shows that as the base-emitter voltage drop increases, the current gain of the transistor rises and eventually plateaus at a ...
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1answer
96 views

Photoluminescence Spectroscopy- Two individual spots, different colors, but same emission spectra

my apologies in advance if I'm not posting at the right site, but StackExchange-Physics is the closest one that relates to this question. Method: Photoluminescence spectroscopy Sample being studied: ...
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1answer
115 views

Band gap energy (discrete or continous?)

What does the band gap energy mean explicitly? Is it a single, discrete energy or is it a energy region? Sketches always show a "gap" between the conduction and the valence band so I assume there are ...
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1answer
140 views

Physics behind depletion region?

I was reading the PN junction. During the formation of PN junction diffusion process takes place in which the free electrons cross the boundary of the P-N and joined with the holes in the P-type to ...
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1answer
17 views

Conceptual doubts with quantum-confined lasers

So, I'm reading about quantum-confined lasers, and I think that I understand the majority of it, but I haven't conceptualized some things that I think are pretty basic. I'll leave this picture here as ...
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1answer
193 views

Why is there a difference between Fermi levels in metals and metal-oxide semiconductors (MOS)?

Why are Fermi levels in metals lower than the Fermi level of $\text{p}$-substrates in metal-oxide semiconductors (MOS)? Specifically, why is there a difference of $qV$? $\hspace{50px}$
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2k views

Non-uniformly doped semiconductor

I am reading Neamen Semiconductor Physics and Devices. In the topic "Non-Uniformly Doped Semiconductor, the author says if there's, let's say, an N-type semiconductor that is non uniformly doped, the ...
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43 views

Wigner-Ekhart theorem for Fermi Golden Rule in semiconductors

I have seen many authors mentioning that there is a way to work in total angular momentum basis and calculate the matrix elements using the Wigner-Ekhart theorem. Here the author even says that ...
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1answer
32 views

Acceptors with very high energy level in semiconductor

I have gallium arsenide (energy gap of 1.4 eV) doped with silicon in concentration of $10^{14} cm^{-3}$ and energy level very close to the conduction band so it's act like a donor. Now we put in also ...
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1answer
74 views

What should be continuous at the interface of two materials, electric potential chemical potential or electrochemical potential?

At the interface between: 1) conductor/conductor 2) conductor/semiconductor (or dielectric) 3) semiconductor/semiconductor (or dielectric/dielectric) What quantity should be continuous? Is it the ...
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258 views

Band structure and Density of states (DOS)

Can someone explain how these two plots are related? How are the peaks in the right are associated with the left figure?
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3answers
846 views

What is the difference between electrons and holes in silicon?

Electrons and holes behave differently in a silicon semiconductor (e.g. mobility of holes is one order of magnitude smaller than that of electrons, the collection time of holes at the same electric ...
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0answers
37 views

How does ambient temperature affect material conductivity

In the book I read I found many contradiction as to how ambient temperature affect material conductivity. Here is an example: Highlighted sentences are cntradictions - "Does any termal energy create ...
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1answer
45 views

Inverse polarization of semiconductors as detectors

I've been reading the particle detector section of the PDG and in point 33.2.3 they talk about Solid-state photon detectors. They say there that Silicon Photodiodes are simply a "reverse-biased p-n ...
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2answers
772 views

In the equivalent circuit of a PN junction diode, why is the battery shown in reverse?

I thought the positive terminal of the battery should correspond to the positive ions in the space charge region. But the polarity shown in the equivalent circuit is in reverse. May I know why this is ...
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28 views

Energy of an electron in the conduction band (semi conductor)

First of all, I'm using the book "Introduction to Solid-State Physics, Charles Kittel, 8th edition". At page 205, he claims that the energy of an electron in the conduction band is : $$e_k = E_c + k^2 ...
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Is there a physical limit to data transfer rate?

Is there a physical limit to data transfer rate (e.g. for USB $3.0$, this rate can be a few Gbit per second)? I am wondering if there is a physical law giving a fundamental limit to data transfer rate,...
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204 views

“Doping” a metal

I had my practical exams today, where I was told to explain the structure and working of a Unijunction transistor (UJT, https://www.daenotes.com/electronics/industrial-electronics/ujt-uni-junction-...
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2answers
1k views

How exactly does the Peltier effect work?

I'm having some trouble finding details on just how the Peltier effect (also known as the Peltier-Seebeck effect or the thermoelectric effect) works on a physical level. Am I correct in thinking that ...
2
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1answer
198 views

Potential drop across PN junction diode in forward bias

If a PN junction diode is connected to a battery, the P part must have a higher potential than the N part(because these points are connected to the battery) and so there should be a potential drop ...
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0answers
22 views

Mathematical way applied to current physical measures to change a spin from $s$=1 to $s$=2?

I read about Spin Modulation in Semiconductor Lasers. I'm interesting to understand better a mathematical way (not physical techniques) applied to current physics technologies measures methods to ...
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2answers
82 views

Is there a relation between Gap energy and Fermi energy?

Are Gap energy and Fermi energy in semi conductors co-dependent variables? If yes, what's the relationship between them?
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1answer
679 views

Why is the silicon crystalline structure is called cubic?

Silicon has a valence 4 (electron shells: 2, 8, 4), hence having 4 neighbors in the 3D space, which for me should appear as a mesh of regular tetrahedrons, with the Si atoms at the centre. But ...
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519 views

Reverse Biasing of pn junction diode [duplicate]

Why can't the electrons that are attracted to positive terminal of cell flow through the wire ?