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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Help understanding why built in voltage in PN junction created?
I was reviewing basic semiconductor physics and need some help understanding where my logic is incorrect. For a basic PN junction, the process of forming the depletion region is described as follows:
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In semiconductors, can distant particles in the same $k$-space recombine? Is this a wave phenomenon, ignoring physical separation?
I'm trying to understand recombination in semiconductors from a wave perspective. I'm considering the wave vector $k$ not just as momentum, but as a descriptor of the wave function's phase. In direct ...
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Temperature coefficient for avalanche breakdown
I am having trouble understanding why is temperature coefficient for avalanche breakdown is positive?
The explanation I found online says as the temperature increase the mean free path decreases ...
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Absorption spectrum in the presence of both dopant and exciton energy levels in a semiconductor
How will the absorption spectrum of a doped semiconductor look if we consider both the dopant as well as the exciton energy levels? And qualitatively, what is the difference between the formation of ...
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Why are valence band and conduction bands parabolic in semiconductor physics?
I was learning about semiconductor lasers where direct and indirect band gap plays a major role in their working, then this doubt struck my mind: Why are valence band and conduction bands parabolic in ...
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How can a transistor behave as a switch in the saturated region? [migrated]
how can a transistor behave as a switch in the saturated region when it is in forward bias mode in the saturation region and the collector current may become zero,
when a transistor is used as a ...
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Apparent contradiction in the definition of Fermi-level
The fermi level in an intrinsic semiconductor is defined as $$E_F = (E_c + E_v)/2 + kT/q \ln (Nv/Nc).$$ From this equation, the position of fermi level is exactly at the center of the band gap at 0K.
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Splitting of states in Semiconductor
According the book "Semiconductor Physics and Devices by Donald A. Neamen",
We have seen previously that, at any energy level, the number of allowed quantum states is relatively small. In ...
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Is the Fermi level taken to be (approximately) constant, i.e. equal to the Fermi energy, in semiconductor physics?
I have been reading Neamen's "Semiconductor Physics and Devices" Chapter 3. He derives in Eq. (3.79) the Fermi-Dirac distribution function
$$f_F(E) = \frac{1}{1 + \exp(\frac{E-E_F}{kT})}, $$
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Characteristics of melanin based semiconductors built from polydopamine
I am curious to know if the relatively newly developed melanin-based semiconductor materials made with polydopachrome have been able to create films or crystals which visually reflect blue, purple or ...
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Optical Properties of Heavily Doped Silicon in the Visible and Near Infrared
I am looking for a model of the changes in the complex refractive index of doped Silicon based on the doping level and type in the visible and near-infrared wavelengths (400-1000 nm). I have seen ...
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Isn't heating insulator enough for sufficient electrons to escape valence band and conduct electricity?
Diamond has about 5.5eV of energy gap, So If I heat diamond it will get atleast 1J energy which is enough to excite about 10^18 electrons, But Diamond still not conduct electricity, Why?
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Why are indirect bandgap semiconductors opaque?
It is commonly explained that semiconductors like silicon, germanium, GaAs... are opaque because all of the visible wavelengths are above the band gap so they get absorbed.
However silicon and ...
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Load Lines and Characteristic Curves
While studying electronic circuits involving diodes, I came across the concept of characteristic curve, which relates the voltage drop in a diode with the current through it. However, I was also ...
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Why do we still consider a doping concentration in undoped MOSFET devices?
I am studying cryogenic behaviour of MOSFET devices especially the evolution of threshold voltage with temperature.
I mostly measure FinFET and FDSOI devices, all which have supposedly undoped channel....
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Do Holes move? ( Solid state electronics physics)
Actually the question that I'm stuck with is related to the holes i.e. the vacant space which occurs when the electron gets displace or move to another position. As holes is the vacant space with ...
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About electricity flow through a diode
I have read answer of Vintage in 11 July 2011 on Krzysztof Lewko's question
Why can electricity flow only in one direction through a diode?
I appreciate very much this answer and i vote as "this ...
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Is there a connection between the differential gain and the spontaneous emission factor $\beta$ in semiconductor lasers?
The section below is from the paper
G. Bjork and Y. Yamamoto, "Analysis of semiconductor microcavity lasers using rate equations," in IEEE Journal of Quantum Electronics, vol. 27, no. 11, pp....
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Carrier concentration on forward biased pn-junction
I understand that when a pn-junction is forward biased minority carriers accumulate and form an exponential charge concentration in relationship to the distance from the junction, as the figure below ...
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Does KVL don't hold in pn junction reverse bias?
Does KVL hold in pn junction reverse bias because any reference about semiconductor physics provide that figure
if we apply KVL around the loop won't be zero it will be equal to $V_{bi}$
then how KVL ...
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Question about k.p Method
I am reading David Miller's quantum mechanics, and I do not understand the derivation for k.p method:
We are particularly interested in the behavior of semiconductors near to maxima and minima.
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Does the built-in potential inside a diode change by making bias?
under thermal equilibrium the pn junction have a built-in field let say it's $E_{1}$ , if we make a reverse bias the external battery provide a permanent field $E_{2}$ , so the total field inside the ...
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Diffusion current because of internal field of semiconductor
Suppose we have an isolated n-type semiconductor having varying concentrations of carriers over x. After some finite time, the concentration becomes uniform for a given constant temperature. We ...
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Metallic behaviour explained by Nearly free electron model
I am having trouble understanding what causes metallic behaviour in context of Nearly free electron model. Is it because
1)
In 2d material with fermi level equation is $k_F=\frac{√2πz}{a}$.
If for a ...
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What would happen if p-type and n-type semiconductor is connected by ohmic contact
I was wondering what would happen if I separate the n-type and p-type regions in a pn junction diode and connect them with an ohmic contact. Or let me put it another way:
Can a pn junction diode be ...
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Why doesn't electron from p junction jump into the conduction band of n junction during reverse bias?
When reverse bias is applied, why can't electrons from p region that are currently occupying the holes jump into the conduction band of the n region, which according to the image (taken from ...
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How does surface area relate to the Seebeck Equation?
I know that the equation is
$$V = (S_B-S_A)(T_2-T_1),$$ but surely this output voltage must be proportional to the surface area (and probably thickness) of the Peltier device. What is the formula that ...
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How does the diode equation hold under forward bias?
In the derivation of the diode equation, the law of the junction is used, allowing us to find the carrier densities across the junction. As pointed out in this question, the law holds only ...
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What is the mechanism of the giant Stark effect?
I do not understand why the band gap shrinks due to the giant Stark effect.
In semiconductors such as black phosphorus, it has been confirmed that the band gap shrinks due to a dc electric field. This ...
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Drift current and diffusion current in depletion region of diode at equilibrium
The diffusion current for a diode at the edge of the depletion region is $I_D=I_S(e^{qV_A/VT}-1)$. Under an unbiased condition$(V_A=0)$ at equilibrium, $I_D$ will be $0$. The drift current should be ...
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What does it mean for semiconductor work function to be p-type or n-type
I want to know what're n-type and p-type semiconductor work function, the difference of work function between semiconductor and metal, and how to calculate n-type and p-type semiconductor work ...
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Why PN junction is needed to detect photons
I am very new to semiconductors and I'm trying to understand how photodiodes work for imaging sensors.
If I am not wrong, a PN junction is required to detect electron/hole pairs that are photo-...
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What is the major challenge in building a hybrid solar panel that uses both PE and PV effects?
In the current times, I see that most solar panels work fully on 'photo voltaic' effect (visible light -> semiconductor). The manufacturers even ensure to block UV as much as possible to increase ...
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Zener diode reverse bias I(V) equation
What is the equation for the reverse bias current in terms of voltage applied? And this even be analytically derived? If so, how to derive it.
I can't seem to find good resources on this topic.
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Integral of diverging function
I'm reading the chapter 10 on excitons of "Quantum Theory of Optical and Electronic Properties of Semiconductors" by Hartmut Haug and and Stephan W. Koch. In the second section of this ...
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Extrinsic semiconductor $𝑇$-dependence
I have the following in my notes:
I dont understand the statement 'simple model fails'
Is the graph shown supposed to be theoretical model or is that the experimental data.
This are equation derived ...
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Why does a single-photon avalanche diode (SPAD) need to be a diode?
Exactly what the title asks. "Diode" comes with it the ideas of depletion layers and forward/reverse biasing and electron-hole recombination, but SPAD physics doesn't seem to be dependent on ...
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Forbidden vs. allowed transitions
In Chapter 1 of his Semiconductor Devices text, Sze gives a crash course (being generous) on solid state physics. At one point, Sze talks about two classes of transitions:
Allowed direct
Forbidden ...
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Physically, up to what size is it possible to miniaturize the process node of a silicon chip? [closed]
With current technology we have managed to manufacture silicon chips of up to 3 nm for the semiconductor industry. To what size is it physically possible to make smaller the process node for these ...
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Current Amplification in Common Base Transistor
How does a common base transistor amplify current if a small part of its emitter current gets divided into base current and the rest goes to collector current? If the input signal is applied to the ...
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Why Energy varies linearly in case of graphene and other Weyl semi-metals and not in conventional semi-metals?
The Energy-Momentum diagram in case of graphene is very unusual as it is conical in shape instead of paraboloid. This means that $E=\mathrm{E}_{0}^{}+ (\hbar^{2} k^{2}/2m)$ is not followed by Weyl ...
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Why did PV cell manufacturing move away from having all of the contacts in the lower end of a PV cell?
In modern day PV cells you usually have a silver-based grid on the upper end of the cell where it's exposed to the sun creating the optimization game of how thin/thick you can make your busbars and ...
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Confusion about how to read the energy band diagram
I am not sure if I understand the energy band diagram correctly. In a pn junction situation below, before the p type material come into contact with the n type material as in figure a), an electron at ...
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Semiconductor Laser
If a semiconductor laser is operated in a DC condition, the injected current is
higher than the threshold, that is to say, the gain will be larger than the overall
cavity loss. So, the stimulated ...
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Graphene characteristics
I am trying to understand the physics of graphene and was unable to understand its I-V characteristics. Could anyone please explain it in simple terms. I have gone through the papers online but couldn'...
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Why is there a linear relationship between the output frequency of a laser diode and the voltage applied to it?
I'm using a tunable laser diode in an undergraduate Rb SAS （saturated absorption spectroscopy） experiment. The product I'm using is the Toptica DLC DL pro, links down below (not an ad). The frequency ...
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Charge density within a PIN diode
Consider the following problem regarding the p-type -intrinsic - n-type (PIN) diode from the Semiconductor Devices fundementals text book:
According to the solution manual the charge density is given ...
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How can the current-voltage relationship of a series of tunneling junctions be most easily derived?
I'm working on a research project with my professor where we're trying to figure out how to determine the necessary semiconductor structure in order for a solar cell to have a particular bandgap in ...
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In-built potential of the pn-junction
I was reading today about the pn junction and there are two things that I don't understand or rather I have no knowledge about.
The first is to know whether the CB of the p-doped semiconductor has ...
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Excess majority carriers in a PN Junction
Current flow in a PN junction is generally expressed in terms of the excess minority carrier concentrations in a PN junction, i.e. the excess holes on the N side and the excess electrons on the P side....
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