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.

learn more… | top users | synonyms

1
vote
1answer
372 views

Why do the drift and diffusion components cancel for each type of carrier if EHP generation plays such big role in p-n-junctions?

I have always argued to myself that drift and diffusion components of the current though a p-n-junction cancel for each type of carrier because any electron diffusing from n into p will sooner or ...
3
votes
1answer
158 views

Why does the Gallum-Arsenite bandgap narrow for higher temperatures and is this because of unavoidable impurities?

I found this sentence: GaAs at 300K contains 10^15 acceptor atoms per cubic centimeter. The bandgaps for Gallium Arsenite are: 0 Kelvin : 1.518 eV 300 Kelvin: 1.424 eV Now I am wondering: ...
2
votes
0answers
359 views

Solving a system of PDE equation in mathematica using a steady-state and time-evolution method [closed]

I'm working to solve the steady-state short circuit current of a solar cells, using the coupled continuity equations with a drift-diffusion expression and Poisson's equation: ...
1
vote
1answer
185 views

Reference for understanding characteristic length and time scales in a system (in particular electronic transport)

I am working on the transport properties of two dimensional electron gas in semiconductor heterostructures and am interested in the characteristic length and time scales of the system like elastic ...
1
vote
1answer
177 views

Why minibands are formed in superlattices?

In a single, finite quantum well, there are energy levels defined by the eigenstates - the solutions of the Schroedinger's Equation. The corresponding wavefunctions leak to the barrier because of its ...
5
votes
5answers
916 views

Derivation of Schrodinger equation for a system with position dependent effective mass

How to derive the Schrodinger equation for a system with position dependent effective mass? For example, I encountered this equation when I first studied semiconductor hetero-structures. All the books ...
2
votes
0answers
987 views

Why is the valence band maximum at the gamma point in the bandstructure view of dispersion relation?

Why is the valence band maximum for most semiconductors at the gamma point in the bandstructure view of dispersion relation
2
votes
1answer
198 views

Does anyone know the difference and relation between $k\cdot p$ method and tight binding (TB) method?

Among the methods of calculating energy bands for crystals, first-principles method is the most accurate. Besides first principles, two commonly used modeling methods are the $k\cdot p$ method and ...
2
votes
0answers
368 views

What is effective mass approximation

Currently i am studing about quantum confinement in semiconductors and came across effective mass approximation.but i am unable to understand this concept. what is the use of effective mass ...
2
votes
2answers
309 views

Problems in the modern semiconductor/electronics technology?

From what I have read, the problem with modern semiconductors/electronics seems to be quantum tunnelling and heat. The root of these problems is the size of the devices. The electrons are leaking out, ...
2
votes
2answers
2k views

Doping of pentavalent atom with hexavalent atom

We know that a tetra valent element can be a semiconductor and doping of pentavalent and trivalent impurities would give a extrinsic semiconductor. I got a question now. Can we use an element of ...
3
votes
4answers
2k views

(If and) Why does cold temperature affect semiconductors?

I had a college student build an overclocked PC using phase-change technology. (This is essentially an air-conditioning unit with the evaporator attached directly to the motherboard.) He said that ...
1
vote
4answers
2k views

Why does a semiconductor hole have a mass?

I have read that holes in semiconductor are nothing but vacancies created by electrons. But how can this vacancy i.e. hole has a mass?
3
votes
1answer
199 views

Confused about charge seperation in solar cells

I'm a bit confused about how solar cells work. My understanding is that there is a p-n junction. A photon is absorbed which creates an electron-hole pair, and the idea is to separate the electron ...
2
votes
1answer
1k views

What does the Fermi Energy really signify in a Semiconductor?

In understanding the behavior of semiconductors, I'm coming across a description of the Fermi Energy here and at Wikipedia's page (Fermi Energy, Fermi Level). If I understand correctly, the Fermi ...
2
votes
1answer
232 views

What is the difference between contact-limited and space-charge-limited charge transport?

I am reading a paper ("Tunable Electrical Conductivity of Individual Graphene Oxide Sheets Reduced at 'Low' Temperatures," Jung, et al. Nano Lett. 2008, 8, 4283-4287) about electrical conductivity in ...
3
votes
1answer
184 views

Theory of Space Charge in a Planar Diode

A planar diode in a vacuum bulb can support current in only one direction. To even get current flowing, you have to heat up the cathode filament to excite the electrons. However, once current is ...
2
votes
1answer
862 views

How is contact resistivity defined for a Schottky contact, or the Schottky barrier height for an ohmic contact?

Based on the transfer length method (TLM), one can accurately calculate the contact resistivity for an ohmic contact, by evaluating the absolute resistance measured through the test structure and ...
1
vote
2answers
175 views

Interpreting range of conductivity diagram

I have found the following diagram (unfortunately in german) about the range of conductivity of conductors (Leiter), semiconductors (Halbleiter) and insulators (Isolatoren). How should one interpret ...
4
votes
1answer
615 views

Turn-on delay time for Laser diode

Do you know any simple explanation on the reason why the turn-on delay time on a laser diode is reducing while we increase the bias current? Turn on delay,is the time that the laser needs from the ...
0
votes
1answer
706 views

Increase of threshold current by temperature in a laser diode

I read somewhere that if we increase the temperature of the material in a laser diode the threshold current for lasing also increases. Can someone explain to me why is this happening? What is the ...
1
vote
1answer
584 views

Physically what happens during Avalanche breakdown to the pn junction?

What does breakdown mean physically? I saw this in wikipedia: The avalanche process occurs when the carriers in the transition region are accelerated by the electric field to energies ...
1
vote
1answer
1k views

change of resistance in semiconductors due to temperature change

I have a question that popped up in an old exam I just can't find a way to solve. If you drop the temperature of this material from room temperature (I guess around 300K) to 0C (273K) the ...
0
votes
1answer
283 views

Equation for finding electrical resistance

I want to know how the flow of electrons will change when I change the tempertature from 100 F to 250 F in a silicon semi-conductor (ex: computer mouse) How can I find this out?
1
vote
0answers
1k views

How to determine donor or acceptor impurity

I am working on a practice exam for semiconductor physics. Can anyone help me figure out how to determine whether we have donor or acceptor impurity in Gallium Arsenide? ...
2
votes
2answers
607 views

Taylor approximation in physics

In a textbook about semicoductor physics, I came across a passage about deriving the carrier concentration at thermal equilibrium in semiconductors I didn't quite grasp: The recombination ...
2
votes
1answer
186 views

Momentum and indirect bandgap

When an electron is excited from valence band to conduction band, it has to have a finite momentum in the case of indirect bandgap. Does that mean that the electron cannot be created at rest ? does it ...
6
votes
6answers
4k views

What are “electron holes” in semiconductors?

I'm tutoring senior high school students. So far I've explained them the concepts of atomic structure (Bohr's model & Quantum mechanical model) very clearly. Now the next topic to be taught is ...
0
votes
3answers
1k views

Indirect band gap semiconductor for LEDs?

Can someone please explain why Indirect band gap semiconductor can not be used for LED creation. Can you also please give me some reference link for details.
2
votes
2answers
4k views

How to make a single crystal silicon wafer?

How can I make a single crystal silicon wafer? What are the tools needed? What is the most diffcult part? Can I make it at home or at school lab? I am now interested on Czochralski process where you ...
6
votes
3answers
13k views

Why can electricity flow only in one direction through a diode?

A few days ago I was soldering a small thing which contained a diode, a battery and some other useless things. Unfortunately, I soldered the diode reversed and it didn't work. When I reversed it ...
3
votes
1answer
665 views

Selection rule used in singlet/triplet recombination in LEDs

In organic light emitting diodes, only singlet excitons contribute to the light emission (this is flouresence). Everything I read, say that triplet excitons cannot recombine on the same timescale as ...
0
votes
1answer
3k views

Ohm's Law and Space-Charge Limited Current

I am trying to understand Space-Charge-Limited-Current (SCLC) and the resulting Mott-Gurney Law. My main problem is conceptual; I don't get why SCLC doesn't produce Ohm's law (j $\propto$ V).
2
votes
1answer
1k views

Fermi-Energy Level for Extrinsic Semiconductor

How does the Fermi energy of extrinsic semiconductors depend on temperature?
4
votes
1answer
2k views

How to determine divergence of a LED source from a single biconvex lens

I'm trying to determine the divergence angle of light from a single lens that is completely illuminated by a high power LED. Most optics textbooks only deal with imaging optics and I'm having a hard ...
3
votes
1answer
422 views

Band offset and strain-induced valence band splitting in semiconductor compounds

My aim is to draw a plot of $GaAs_{1-x}Sb_{x}$/InP (GaAsSb on InP substrate) band offset as a function of As/Sb composition. The first part is easy if I'm doing this correctly: I found VBO (valence ...
3
votes
1answer
380 views

III-V semiconductor compounds - band gap approximations

I'm looking for the most common and accurate approximation functions for III-V semiconductor compounds. So far, I found two (InGaAs as the sample compound): The simplest one: ...
1
vote
0answers
411 views

Fermi level in disordered amorphous and/or organic semiconductors

So, the Fermi level in crystals is pretty easy to understand. Been using it and talking about it in terms of the highest occupied level forever. However, I'm now reading about disordered systems. A ...
3
votes
2answers
333 views

Purchasing semiconductor substrates

I'd like to make a comparison of prices, availability and properties of semiconductor substrate layers like Si, Ge, GaP, AlN etc. I wonder what are the problems related to getting such data, what are ...
3
votes
1answer
598 views

Energy levels in disordered organic semiconductors?

Now in disordered organics, the band picture is thrown out the window, from what I can tell (due to lack of symmetry). But don't HOMO/LUMO levels basically take the place of conduction/valence bands ...
5
votes
2answers
2k views

What's a typical electron-hole recombination time of semiconductors?

Have some trouble finding a useful reference to answer the following questions: What's a typical electron-hole recombination time of semiconductors? And how does it depend on the temperature and the ...
8
votes
2answers
739 views

Modern and complete references for the $k\cdot p$ method?

I've recently started studying the $k\cdot p$ method for describing electronic bandstructures near the centre of the Brillouin zone and I've been finding it hard to find any pedagogical references on ...
4
votes
1answer
3k views

What is injection level (semiconductor physics)?

I am currently reading journal articles about semiconductor physics in solar cells. What is injection level? I'll try to start off with what I understand. Photons hitting the silicon cause its ...