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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Fermi-Dirac function electron and hole concentration

I have a question regarding the Fermi-Dirac function. I would like to confirm that my basic understanding is correct. Is any space under the curve in the CB and VB describe the probability of finding ...
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38 views

How do I calculate the electrical conductivty of arbitrary semi-metal?

Assume that I have an Hamiltonian $$H=\sum_{k,\sigma}a^\dagger_k E(k)a_k$$ where $E$ is the dispersion relation with gap closing at some points. I want to calculate the conductivity of this system. To ...
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86 views

Please grant me an accurate explanation of diode reverse bias mechanism

Consider the image above. Now I am an electron in that depletion region. I was not here initially, I was in the wire (free-moving electron of a copper atom) or perhaps battery (...of an ion?) but now ...
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238 views

Insight into holes as charge carriers in semiconductors

I can't seem to get my head around the idea that both electrons and holes are charge carriers in semiconductors. Surely holes are just lack of electrons. Is it true to say that there are two ...
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353 views

Why is voltage gain highest in common base transistors whereas lowest in common collector transistors?

Although the common base transistors have current gain lowest and the common collector transistors have current gain highest.
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Self-consistently solve coupled Poisson-Drift Diffusion eqns. for semiconductor device analysis

I have a system of coupled non-linear ODEs. $$J = \mu e \left( n(x) E(x) + \frac{K T}{e} \frac{dn(x)}{dx}\right)$$ $$\frac{dE(x)}{dx} = \frac{4 \pi e}{\epsilon}[N_D(x) -n(x)]$$ The first ...
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27 views

Solar photovoltaic diode current flow

When the PV cell is provided an external circuit, why do the electrons flow through the wire even when it can flow directly from within, between the p and n side? What happens to the generated ...
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273 views

Energy level splitting in a semiconductor

In the above image, I see that the graph curves upwards in a weird manner from $b$ to $0$. ( middle graph) I understand the reason that the graph splits from a single energy line to a ‘band’ of ...
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124 views

Where does forward voltage drop in a diode?

To simplify the picture, I would start with an n-type Schottky diode. It has two junctions: one rectifying and one non-rectifying (ohmic contact). When the diode is forward biased, it conducts ...
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57 views

Different Color Intenensities from simple ON/OFF RGB subpixels

I recently got interested in electronic paper. One design that I liked was the one from Mirasol: https://en.wikipedia.org/wiki/Interferometric_modulator_display However, what I don't understand, is ...
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64 views

Conventional explanation of basic Semiconductor & Diode behavior unconvincing

I have seen this and this and a few other. Throughout the web and notes I find the explanation of the workings of a simple diode sort of unconvincing and I am depressed by the fact that I am not able ...
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55 views

what is the origin of minority carrier in semiconductor?

I am analyzing particular type of radiation detector which is used in medical imaging device.The depletion layer and minority carrier plays a big part of the charge collection process, specially the ...
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700 views

How diffusion and drift current in a PN junction get equal?

Let's consider a PN junction which is at zero biased voltage. Once the junction is formed charges are diffused across the junction and form the depletion region and stops further diffusion. So no ...
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64 views

Circuit Analysis - Grounding and Current

Just starting to learn basic concepts of electronics, and I'm a bit confused looking at this diagram. Previously, we've always had a wire connected to the negative end of the terminal, and that made ...
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Optical Conductivity and Scattering rate - Physical intuition

Why does the real part of conductivity increase with increase in scattering rate at frequencies much larger than the scattering rate? I understand the mathematical implication, but do not understand ...
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32 views

Similar diodes in bridge rectification

Why are similar kinds of diodes used in bridge rectification ? What will be the problem if different kinds of diodes are used ? My book says that , the oscillation of current through circuit would ...
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155 views

Reason for a thin base of transistor

I have been recently asked the following question: Why is the base of a transistor kept thin? MY ASSUMPTION Base is kept thin so that not many charge carriers could be neutralized in the process ...
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524 views

Depletion region width in forward bias

In forward bias the electrons from n region move to p region after crossing the depletion region and holes from p region move to n region. But shouldn’t they recombine and hence the width of the ...
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Problem of measuring barrier potential by a voltmeter

I have read in my book that The barrier potential of a diode junction cannot be measured by a voltmeter only. It says that the thermal equilibrium is disrupted. Besides , the contact potential is also ...
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64 views

How to see s, p, d, and other band in the band diagram? Is it possible?

I am reading this book, to understand magnetism in material. It is stated there that the d-bands overlap the next higher s-band. I am aware about Hund's rule. How to see that in the band diagram? ...
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Do donor atoms leave holes?

I was reading text about n-type doping and it said: 'Such impurities are called donors for they donate electrons. Notice that in this case, no hole is created in conjunction with the creation of a ...
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46 views

Help with $I$-$V$ Characteristic of a Diode

I am struggling to understand why I can't get a full voltage range when I have the diode the correct way round. If you check this link: https://electronics.stackexchange.com/q/266201/ If you look at ...
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29 views

2D Electron Gas interface of two semiconductors

I am looking at a book or paper describing the theoretical description of a 2D electron gas formed at the interface of two semiconductors. I have encountered many experimental realisations of 2D ...
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162 views

How would I determine or calculate the metal work function of an alloy

I am trying to build a schotky diode but based on a little bit of physics that I might use for kids at a high school. Specifically to build a point contact/cats whisker diode. From the theory I have ...
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75 views

Saturated BJT Transistors. V CE < V BE : AKA - Things that make you go “Hmmmm”

At the risk of being blasted for cross-posting, I am posting this question again here in the Physics department. It is a duplicate of this post in the EE forum. However, I would like to get some ...
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51 views

Why is the input characteristic curve almost independent of $V_{\text{CE}}$?

I am studying the Input Characteristic curve in an $n-p-n$ transistor in common emitter configuration (high school level). My book (NCERT) gives the following curve: for this circuit diagram: I've ...
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Saturated BJT Transistors. $V_{CE} < V_{BE}$ : AKA - Things that make you go “Hmmmm” [duplicate]

We use them every day and those in the know fully understand the functional characteristics of BJT transistors. There are documents and links galore explaining the operational math. There are even ...
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52 views

Reorganization of energy bands beyond a very low lattice constant

I read this (from this website, with my emphasis): As the lattice constant is reduced, there is an overlap of the electron wavefunctions occupying adjacent atoms. This leads to a splitting of the ...
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150 views

p-n junction depletion region

My Textbook reads: During forward biasing, holes move towards n side and electrons move towards p side. The diffusion of electrons and holes into the depletion layer decreases its width. If more ...
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135 views

Cosmic ray shielding for electronics on Earth

There are plenty of topics discussing cosmic ray shielding, but they all put emphasis on spacecraft shielding, where things like radiation and mass are a big problem. So I decided to ask a question ...
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435 views

Hall-Voltage behaviour with increasing temperature

I have a question relating to this diagram: It shows the relationship between Temperature and Hall-Voltage of a P-doped Germanium Plate. The electron density n is constant from 10°C to 50°C, that's ...
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190 views

How to determine the activation energy for donors/acceptors using the Arrhenius eq.?

I am trying to determine the donor/acceptor activation energy for the semiconductor InGaP with the Arrhenius equation. However it contains only one parameter for the activation energy, which turns out ...
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909 views

Derivation of hall coefficient for semiconductors

I was wondering how hall effect works in semiconductors. While looking up in the internet, I came across the following formula for the hall coefficient $R_H=\frac{E}{jB}$ in Wikipedia ($E$ is electric ...
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150 views

How does a gate voltage determine the state of a transistor?

It is known that in a transistor, like the FET below, it has an 'on' state when current flows from source to drain, and an 'off' state when there is no current flowing between junctions. This current ...
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89 views

What does $k$ stand for here?

We know that diode equation is $$I_d=I_S(e^{V_d/nV_T}-1)$$ where $V_T$ is the thermal voltage acquired, given by $V_T=kT/q$. But what does this $k$ stand for? The value of $k$ is given as $1.38 \...
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Mass-Action Law

So,here's the equation of Mass-Action Law:- $ np =n_i^2 $ Here, $ n= $ Electron Charge Density ; $ p= $ Hole Charge Density And, $ n_i^2= $ Intrinsic Charge Carrier Concentration The equation is ...
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252 views

Effect of magnetic field on energy gap of semiconductors like diode, transistor

I am doing my project on energy gap of semiconductors. For that i have an doubt that what will happen to the energy gap of diode if it is exposed to magnetic field intensity? Is it possible to place ...
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136 views

Is electron-hole pair generation and recombination process in insulator same as semiconductors?

I was trying to understand the electron-hole generation and recombination process in materials. However, most of the sources explain the phenomenon by using semiconductors through the energy-band ...
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164 views

electron-hole pair recombination

Please I will like to know if a reasonable amount of heat can be generated upon the recombination of an electron-hole pair in a photo-excited semiconductor nanoparticle (such as TiO2, CeO2). Thanks ...
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Semiconductors : LED [duplicate]

I got to know that the threshold voltage for an LED is different for LEDs emitting different colors. I don't actually know the reason. I searched everything from the Web but didn't get that... Kindly ...
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35 views

Semiconductors: LED

My book mentions that, "the bandwidth of light emitted by an LED is $100$ angstrom to $500$ angstrom or in other words (but not exactly) monochromatic". What that supposed to mean? Is that mean the ...
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52 views

Specifics of the current flow in a tunnel diode

Those are two diagrams depicting current flow along with equivalent band diagrams form two different textbooks. I believe one first one is resonant diode and second is tunnel diode only. From the ...
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141 views

Semiconductors : Zener Diode

I was wondering how a large current flows after a small change in the zener breakdown voltage. I know why it happens at the zener voltage, but my book says that even after insignificant change in the ...
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55 views

Understanding the principle of photo diode signal generation

I have two lasers, both illuminate on a photo diode, i'm not very sure what's physically going on in the photo diode. My understanding is the following: The electric fields of both lasers add up and ...
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464 views

Metallurgical Junction

I've been studying p-n junction. Then came the term "Metallurgical Junction". What's that? Metallurgical? I know its the study of metals and their properties. But why this is there in semiconductors? ...
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1k views

Finding number of electrons in n-type semiconductors [closed]

I'm having numerical problem based on n-type semiconductors: Suppose a pure Si crystal has $\mathrm{5 \times 10^{28}\ m^{-3}}$. It is doped by $1$ ppm concentration of pentavalent As. Calculate the ...
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65 views

Semiconductors: Movement of Hole current

It's a lot of confusion!, seriously! lot of-! The holes, the charge carriers in p-type semiconductors. Right? But what if all the holes, all of them travels to the negative terminal? What about the ...
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Semiconductors: Hole current

...And then suddenly It came in my book, Hole current is also there in semiconductors and i know it. But there's a little thing that's confusing me. Is this hole current temporary? Yes, according to ...
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588 views

BAND THEORY : Overlapping energy bands in metals

I have been studying Energy bands and suddenly I encountered a diagram in which the two bands(valence and conduction) overlaps in case of metals. What is the meaning of this overlapping? Suppose they ...
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92 views

Heating a semiconductor device

My book(this is my book, page $468$) says this thing: No external heating is required by a semiconductor device I'm confused. I know silicon conducts electricity when it is heated. So, why heating ...