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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266 views
Capacitance per unit area and CMOS case
In a modern 0.35μm CMOS processor, the gate oxide thickness is around 80Å = 8nm. This gives us a capacitance per unit area of $430nF/cm^2$
I am not getting how one gets this capacitance per unit ...
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2answers
103 views
The direction of electric field in a diode
Why electric field pointing to left? (The middle area is depletion region.)
(This is without any external electrical voltage applied.)
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2answers
564 views
Current through the reverse biased junction in transistor
A transistor is a three terminal device. One terminal is called emitter, one collector and in between them is base. Now, during biasing the junction between emitter and base is made forward biased and ...
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1answer
112 views
Semiconductors and localization of the electrons
When looking at the band diagram of a semi-conductor, direct conclusion of the invariance under discrete translations, for a filled state with an electron, one does know precisely it's momentum, so my ...
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0answers
100 views
Physics understanding of MOSFET and CMOS [closed]
CAn anyone provide me some clear links or explanation regarding physics understanding of MOSFET and CMOS? I know CS logic understanding - but I want to know how MOSFET and CMOS are created, and how ...
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1answer
77 views
How creation of point defects in semiconductors is affected by strain?
When the effect of the strain on solids is discussed, normally the explanation is the following: increasing stress, first point defects created, then dislocations, then plastic deformation starts, ...
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1answer
48 views
Charge carrier injection in heterostructures - help with concept definition
I have this report to do on "Charge injection in heterostructures". I have been searching and reading but I still have some trouble with the basics, i.e. defining the concept.
As far as I understood ...
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1answer
738 views
Characteristic of a common emitter transistor [closed]
How is Base emitter junction and collector emitter junction biased? How do we determine the value of potential difference between emitter and collector required to be maintained in order to determine ...
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1answer
82 views
Semiconductor problem: how much Boron is required to establish a certain amount of charge carrier density
The problem description is as follows:
Boron is used to dope 1 kg of germanium (Ge). How much boron (B) is required to establish a charge carrier density of 3.091 x 10^17 / cm^3. One mole of ...
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2answers
154 views
how does zener diode maintain potential across its terminals?
My physics book has a topic about zener diodes being used as voltage regulators in the reverse bias.
Well, I'm curious to know how does the zener maintain the potential across its terminals after it ...
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1answer
128 views
Metal rod between a capacitor
In my experiment, I am filling liquid crystal between two glass plates. Nn AC voltage is applied on them. The thickness of the liquid crystal cell is around $200 \mu m$. One glass plate is with +V and ...
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0answers
55 views
Quantum Mechanics Text for Electrical Engineers [duplicate]
Possible Duplicate:
What is a good introductory book on quantum mechanics?
What is a good introductory text on quantum mechanics that could be used to train electrical engineers in device ...
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1answer
142 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 ...
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0answers
55 views
Reducing and re-Oxidizing Titanium Dioxide [closed]
I'm having a hard time finding data about an experiment that I know has been done a bunch of times:
I have a sheet of rutile TiO2 (110) that I want to reduce to various TiO(2-x) forms where the x is ...
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1answer
61 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:
...
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0answers
173 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:
...
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1answer
76 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 ...
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1answer
70 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 ...
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5answers
528 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 ...
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329 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
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0answers
120 views
When the p-n junction of a transistor is reverse biased? [closed]
When the p-n junction of a transistor is reverse biased?
A. current flows from the p-type to the n-type.
B. no current flows from the p-type to the n-type.
C. conduction of current occurs.
D. ...
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1answer
105 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 ...
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0answers
204 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 ...
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0answers
72 views
Charge Based Capacitance Measurement (CBCM)
I am using Keithley 4200-SCS to measure the device capacitance.In order to get total capacitance of the device, the Gate terminal is voltage biased and the other three terminals are grounded.
I wanted ...
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0answers
100 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, ...
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0answers
93 views
Energy efficiency Vs power efficiency
I want to understand if there can be any real difference between the requirement of Energy efficiency and the requirement of power efficiency for a physical system. For example for CMOS-based digital ...
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1answer
446 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 ...
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4answers
480 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 ...
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3answers
468 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?
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1answer
130 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 ...
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1answer
340 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 ...
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1answer
85 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 ...
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1answer
105 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 ...
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1answer
458 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 ...
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2answers
110 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 ...
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0answers
238 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 ...
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1answer
293 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 ...
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0answers
144 views
Plot of electric potential inside a p-n junction for nonzero bias [closed]
I'm looking for a plot/cartoon of the electric potential inside a p-n junction that is under forward or reverse bias. Something just like ...
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1answer
255 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 ...
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1answer
753 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 ...
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1answer
196 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?
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0answers
109 views
How did Shockley, Bardeen, and Brattain get purified germanium and dope it correctly?
They obviously didn't have precision semiconductor fabricating tools themselves running with semiconductor parts inside because there were none. We have so much advanced machinery to weigh out, ...
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0answers
367 views
On what does the breakdown voltage of zener diode depend on [closed]
On what factor does the breakdown voltage of zener diode depends
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0answers
386 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?
...
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2answers
451 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 ...
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1answer
153 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 ...
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6answers
2k 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 ...
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3answers
402 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.
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2answers
2k 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 ...
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1answer
519 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 ...
