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 affect it.

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Search materials by HOMO, LUMO and work function [on hold]

I need to search organic semiconductors for organic photovoltaics (OPV) by their HOMO, LUMO, work function (WF) at 300 K (as I understand, WF cannot be derived from HOMO and LUMO because semiconductor ...
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Does doping silicon affect its coefficient of thermal expansion (CTE)?

Everywhere I have searched I always see the CTE of silicon listed as 2.6*10e-6 °C^-1. However, I have silicon that was phosphorus-doped to an ion concentration of of 2.41*10e11 atmos/cm^3, and I would ...
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Ohmic contacts in a diode (metal-semiconductor junction) - contact difference of potential $V_0$ - how to compute

I'm reading "Microelectronics" by Millman, Grabel. Premise: The book developed, for a pn step-graded junction, the contact potential as $$ V_0 = V_T \text{ln} \frac{p_{p0}}{p_{n0}} = - V_T ...
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AC Stark effect first order change in energy

I am looking at this paper http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=89946 where Eq (12) $\triangle E_{ii}(\tau)=-\frac{e\hbar}{m_{i}c}\bf{k}.\bf{A}(\tau)$ (where i=c,v) is mentioned as the ...
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Is the built-in potential in a PN junction the same as the “knee” or “turn-on” potential?

Considering a PN junction with a difference in fermi level between the P and N type regions given by eV0. Does this V0 correspond to the potential at which the diode "switches on"? My intuition tells ...
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25 views

How is the bandgap reference diode so accurate? (temperature changes bandgap?)

I am studying about bandgap references (wiki). As a black box approach, (from what I know) it can be seen as a system which gives a stable voltage reference irrespective of the highly varying ...
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35 views

Topology of a bit

From a math perspective, it seems obvious that the electric field (or voltage which ever) of a bit in a computer, when its in a stable 0, or 1 state, must have a singularity, a set of points where the ...
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What limits the doping concentration in a semiconductor?

Si and Ge can be blended in any ratio, $\mathrm{Si}_x\mathrm{Ge}_{1-x},\ 0\le x\le 1$. So do InxGa1-x. So what exactly causes doping impurities inside Si/Ge/etc. to saturate at $\sim 10^{-19}\ ...
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Can a strained diamond actually become conductive?

According to about.com, "The electrical resistivity of most diamonds is on the order of 1011 to 1018 Ω·m" (source) However, according to the diamond band diagram, it seems that under a certain ...
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Graded semiconductors - hole concentration function of x

I'm stuck at page 37 of the (second ed.) of "Microelectronics" by Millman & Grabel, section "1-7 Graded Semiconductors". Before that section, it spent some time explaining the phenomenon of ...
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41 views

Semiconductors and energy bands

The valence and conduction band of a semi-conductor are often drawn as here click. This plot has essentially two features and I would like to understand them. The peak and the valley of the two ...
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70 views

3D Density of states

I have the following dispersion relation: $$\epsilon(\vec{k})=\frac{\hbar}{2}\left(\frac{k_x^2}{m_1}+\frac{k_y^2}{m_2}-\frac{k_z^2}{m_3}\right)$$ (note the minus sign in the third term). And I am ...
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24 views

Periodic momentum space in band structure

I often see pictures like this in physics, this one for Silicon band structure. (source, NB: it's the German page for Silicon). There you see the plot of the energy in terms of the momentum $k$. ...
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46 views

Hole, solid state physics

In n-type semi conductor, when hole is created, which starts to move, but not in p-type semi conductor, hence, is a hole a static or dynamic? hole is absence on electron, absence means nothing, then, ...
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20 views

Exciton in semi-conductor

I don't understand why an exciton describes only the interaction between an electron hole and an electron in the conduction band? How is this interaction different from the interaction between an ...
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39 views

Why are laser pulses Sech Squared in temporal shape?

Ultrashort pulses from mode-locked lasers often have a temporal shape which can be described with a squared hyperbolic secant ($\mathrm{sech}^2$) function: $$ P(t)=P_0 \mathrm{sech}^2 \left( ...
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Why an undoped heterojunction causes potential barrier?

In this image (source) a potential double-barrier was created using GaAs and AlAs lattices (undoped). Why would any potential barrier be formed, if all the bonds are electrostatically balanced (i.e. ...
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Why the current through a resonant tunnel diode drops when the bound state goes below the conduction band?

The IV curve of a resonant tunneling diode is N-shaped. The rise in current flow happens because the bound state (the energy state in the well) enters the thermal area of the conductor ($\mu_1 + ...
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Why a tunnel diode (TD) is called a diode?

Traditionally, a diode is a 2-terminal device that limits current to flow in one direction, i.e. a rectifier. But a "tunnel diode", according to wikipedia, is not rectifying: In the tunnel diode, ...
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Thermal conductivity of semiconductors - theoretical function?

Below is a plot of the thermal conductivity coefficient for Gallium Arsenide, reproduced from 3: I would like to interpolate the data, but I don't know what fit function to use. I tried a generic ...
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Crystal structure of Silicon

From what I was reading, Silicon has a FCC unit cell but they also said that the Silicon atoms form a tetrahedron at 109 degrees from each other. Then they said that the tetrahedron is formed by ...
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Lattice and carrier temperature

If I hold a semiconductor sample at a certain temperature $T$, its lattice temperature $T_l$ will equalize: $T_l=T$. But how is this lattice temperature related to the carrier (electron or hole) ...
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60 views

Question on Shockley's equation for FETs

I'm currently studying FETs (Field Effect Transistors) in Navy school. What I know so far is that in FETs, $V_{gs}$ is reversed biased, creating a depletion zone. What this means in plain English is ...
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41 views

Why don't electrons simply diffuse back when illuminating a photodiode?

Assuming you connect the cathode and the anode with a conductor (no sources), why can't the electron-hole pairs created by the photons diffuse back instead of going through the wire? My reasoning is ...
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Couting the occupied states in band structure

I work with several dft codes and I have produced the band structures of some doped semiconductors with their plots. The problem I have is that I do not know how I can analyze the band structure and ...
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A question about Memristors

A question about memristors: These semiconductor entities have been defined in terms of magnetic flux leakage, and a non-linear relationship to the electric charge that has flowed. In essence, the ...
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What makes Monocrystalline silicon a good semi-conductor? [closed]

I'm researching Monocrystalline silicon for a school project and focusing on its application in Electronics. One area I'm researching is why the material is a good semiconductor, and what properties ...
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33 views

Why is the heavy/light hole band not called heavy/light electron band?

Are the bands called heavy hole, light hole and electron band, just because the charge carriers are holes/electrons or is there some deeper reason I missed? The question might seem stupid, but it ...
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23 views

Semiconductor band diagram with a doping gradient

What does the Energy band diagram in a semiconductor look like if we introduced a doping gradient? What would it look like if after we added the doping gradient we introduced an electric field? I ...
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Discrepancy in introducing Schottky barrier

I have a problem regarding introduction of Schottky barrier in metal-semiconductor junction. Because of this barrier the energies of conduction band vary discontinuously and hence the potential is ...
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2answers
57 views

Surface acoustic wave

Why does a surface acoustic wave (SAW) propagate only in the surface leyer of the solid, let's assume a semiconductor? One can create such a SAW through an interdigital transducer (IDT) as I read, ...
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80 views

Calculating Boltzmann constant using semiconductor

My task from the latest laboratory exercise in physics is to calculate Boltzmann constant from known temperature, current and voltage. We were given this circuit: By changing the resistor value, I ...
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What's so special about the invention of Blue LED that a Nobel was awarded to its invention? [duplicate]

Why was this years Nobel Prize for Physics awarded to Isamu Akasaki, Hiroshi Amano, Shuji Nakamura for inventing the Blue LED? I know that if a Nobel Prize is awarded for an invention, it must be ...
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Why in PN junctions the octet rule is dominating electrostatic repulsion?

The depletion region in PN junctions is created by charges from the N part diffusing into the P part, thus completing an octet of covalent bonds in the P part. This shift however leaves positive ions ...
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Why do we have Indirect bandgap semiconductor?

If the energy of an electron is proportional to square of the momentum k, how come we have a Indirect Bandgap material in which the minimum of the energy in conduction band is not at k not zero. P.S. ...
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Why the minority carrier lifetime is different for electrons and holes?

The lifetime of minority carriers ($\tau_n$ for electrons, $\tau_p$ for holes) represents the average time before recombination. But since an electrons must have a hole for recombination to take ...
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Has the Nobel committee mixed up this years prizes for Physics and Chemistry? [closed]

The title of the question is tongue-in-cheek but the question remains: How does the Nobel committee delineate the fields when awarding work which is of such an inter-disciplinary nature. The chemistry ...
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Nobel prize for (dangerous) LED lamps? [closed]

There are many scientific articles about the danger of LED lamps (see below from the LED magazine, from scientific american, from a governmental journal and from Harvard health newsletter): Light ...
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Why does Fermi level has a probability density of 1/2 while it may lie in the forbidden region?

I dont understand how there is a continuous probability density function in semiconductors, when there are several regions which are restricted by Energy, i.e. forbidden energies. Well i know that in ...
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Complex dielectric constant in ultraviolet range

Dielectric constant of a material could be a complex number, which is dependent of the frequency of electromagnetic wave. From the Springer material website, I learn that both the real part and ...
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Why does the width of the depletion layer in a semiconductor change with the amount of doping? [duplicate]

I've read that if there is very low doping in a pn-junction diode, the depletion region will be large because a large volume of depleted semiconductor is needed to generate enough electric field to ...
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141 views

Effect of doping on the width of depletion layer of PN-junction diode

I've read that if there is very low doping in a pn-junction diode, the depletion region will be large because a large volume of depleted semiconductor is needed to generate enough electric field to ...
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1answer
34 views

Size of bit cell in flash memory

If we consider a normal sd card, whose dimensions are 11x15x1 $mm^3$, there are 512,000,000,000 bits stored in 64 GB memory card. If one bit is stored per cell, size of a cell would be 10e-14 m on ...
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Why is the law of the p-n junction valid under forward bias?

I'm currently studying the physics of the PN junction. I went though the derivation of the built-in potential in the PN junction under equilibrium: $$ {Diffusion\ current\ density} = {Drift\ current\ ...
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2answers
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Why is nitrogen not used as a pentavalent impurity?

I don't understand why nitrogen though a fifth group element is not used as a pentavalent impurity in doping a semiconductor.
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Can electrons move back into the donor level

In a n-type semiconductor electrons from the donor level move up into the conduction band but can they move back down? Also in a p-type semiconductor electrons move to the acceptor level from the ...
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N-type semiconductors and the number of holes?

Let us say we have Germanium which has been doped with antimony. Antinomy has a a fifth valence electron not involved in bonding. Is this electron in the valence band? I ask because all texts on the ...
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How do we predict electrical properties of a material using scattering data and vice-versa?

I know that the band gap is related to conductivity. What I'm wondering is what it is like for an experimentalist who is trying to figure out what an unknown material, a black box, is doing. The only ...
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Does the Shockley Diode Equation hold in a dynamic circuit?

Consider the following simple photodiode circuit: I've created a real-life version of this circuit, and I've detected that $I$ is oscillating: $$I(t)=I(t+\tau)\tag{$\tau\approx ...
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Silicon/silicon dioxide interface

Suppose we have an interface of silicon/silicondioxide. If we shine light on the top surface electron-hole pairs are generated in silicon. since there is always a field directing from surface to bulk ...