What is Semiconductor: Definition and 397 Discussions
A semiconductor material has an electrical conductivity value falling between that of a conductor, such as metallic copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. Its conducting properties may be altered in useful ways by introducing impurities ("doping") into the crystal structure. When two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers, which include electrons, ions and electron holes, at these junctions is the basis of diodes, transistors and most modern electronics. Some examples of semiconductors are silicon, germanium, gallium arsenide, and elements near the so-called "metalloid staircase" on the periodic table. After silicon, gallium arsenide is the second most common semiconductor and is used in laser diodes, solar cells, microwave-frequency integrated circuits, and others. Silicon is a critical element for fabricating most electronic circuits.
Semiconductor devices can display a range of useful properties, such as passing current more easily in one direction than the other, showing variable resistance, and sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion.
The conductivity of silicon is increased by adding a small amount (of the order of 1 in 108) of pentavalent (antimony, phosphorus, or arsenic) or trivalent (boron, gallium, indium) atoms. This process is known as doping and the resulting semiconductors are known as doped or extrinsic semiconductors. Apart from doping, the conductivity of a semiconductor can be improved by increasing its temperature. This is contrary to the behavior of a metal in which conductivity decreases with an increase in temperature.
The modern understanding of the properties of a semiconductor relies on quantum physics to explain the movement of charge carriers in a crystal lattice. Doping greatly increases the number of charge carriers within the crystal. When a doped semiconductor contains free holes it is called "p-type", and when it contains free electrons it is known as "n-type". The semiconductor materials used in electronic devices are doped under precise conditions to control the concentration and regions of p- and n-type dopants. A single semiconductor device crystal can have many p- and n-type regions; the p–n junctions between these regions are responsible for the useful electronic behavior. Using a hot-point probe, one can determine quickly whether a semiconductor sample is p- or n-type.Some of the properties of semiconductor materials were observed throughout the mid 19th and first decades of the 20th century. The first practical application of semiconductors in electronics was the 1904 development of the cat's-whisker detector, a primitive semiconductor diode used in early radio receivers. Developments in quantum physics led in turn to the invention of the transistor in 1947, the integrated circuit in 1958, and the MOSFET (metal–oxide–semiconductor field-effect transistor) in 1959.
I did an experiment with Indium antimonide (InSb) in Liquid Nitrogen. I turned the sample one way in the B field and took a reading of the voltage (positive) and turned it 180 degrees and took a reading of voltage (positive, and a greater value). I use V_h = v1 - v2 / 2 and I get negative values...
Hello all !
I'm trying to solve a problem (link below)
i have a problem to define the energy(s) distance {exp numerators} so i can't insert to the values needed into the equ. i wrote down.
any help would be great !
http://rapidshare.com/files/406858775/ex3.pdf"
TNX !
Hi Everyone!
There are some things about semiconductors that have always puzzled me,and I think it's high time I got them cleared up!
Here are my four questions...please help.
1. When an impurity atom (dopant) is added to an intrinsic semiconductor,(say germanium),is the band structure...
Homework Statement
in Intrinsic GaAs,electron and hole mobility are 0.85 and 0.04 meter square/volt-sec
and corresponding effective mass are 0.068m and 0.5m, where m=9.11*10^(-31)kg.
band gap energy is 1.43 eV at 300K.
---calculate intrinsic carrier concentration(!) and Conductivity.
Homework...
what really makes a semiconductor? Is it just the presence of a band gap but then insulators and metals also have band gaps or carrier concentration? Or we need to perform Hall measurements and also need to study I-V characteristics? Or do we need all of these parameters to establish a material...
doubt in semiconductor diode theory ?
hello friends :smile:...
in this picture diode is forward biased. positive terminal of battery repel holes n negative repel electrons , finaly electrons n holes recombine n eliminate each other.
but its said that current flow is due to electrons ...
I'm wondering how one would go about measuring the conductivity of a semiconductor with variation in temperature, I assume the non ohmic behaviour prevents one from making simple voltage current measurements and then inferring resistance and the conductivity...any answers much appreciated...
Hi, I want to know what the important quantitative differences between the light produced by an atomic gas laser and that produced by a semiconductor laser are?
I know that produced my atomic gas lasers are low power but high collimation, but semiconductor lasers seem to have higher power...
Hi, I want to know what the important quantitative differences between the light produced by an atomic gas laser and that produced by a semiconductor laser are?
I know that produced my atomic gas lasers are low power but high collimation, but semiconductor lasers seem to have higher power...
Homework Statement
Consider a model semiconductor with a bandgap of 1.0 eV which is doped with 10^17 /cm^3 acceptors for x<0 and 10^17 /cm^3 donors for x>0.
E_c - mu = 0.1 eV on the far left and on the far right (far from x=0)
Homework Equations
The Attempt at a Solution...
A question on semiconductors.
I need to determine the carrier concentration and type.
I have worked out the type but its the conc. that is getting me.
I have the conc., n, as:
n = wBJ / eV
w is the width of sample, B the mag. field, e is charge, and V the Hall...
Homework Statement
I am asked to show that the conduction electron density in an n type semiconductor is given by:
n=\frac{1}{2} \left( -n_0 e^{-(E_c-E_d)/kT} + \sqrt{n_0^2 e^{-2(E_c-E_d)/kT}+4 n_0 N_d e^{-(E_c-E_d)/kT} } \right)
where
n_0=2(m^* kT/2 \pi \hbar^2 )^{3/2}For low temp p=0 and...
hi, I am reading my notes on semiconductor physics and this is a concept that is puzzling me - i always thought a vacancy and a hole were the same thing.
in my notes it says that
a hole has the same properties as a full band with one vacancy and so for consistency the hole must have...
Hello!
There're very thin (4-15 nm) semiconductor films (passive film) formed on stainless steel by electrochemical method. In a electrochemical cell, I applied potential on stainless steel electrode to adjust Fermi level of the semiconductor passive film. I think that band bending take place...
P type semiconductor coil...
The magnetic field orientation in a P type semiconductor wire, in which a DC current is flowing will be caused by the direction of movement of the electrons or the positive holes?
So, I am doing a little bit of research on how energy is created in solar cells. From what I understand, there is just a whole bunch of n and p junctions connected to each other electrons flow the same way. Or, electrons travel one way, and holes travel the other. So when you dope the silicon...
Suposse you have a material you are told is semiconductor, but don't know any more history about the material. What experiment(s) can be performed in order to find out if your material is direct or indirect?
Homework Statement
Q1
A Si sample is doped with 10^16 per cm^-3 boron atoms and a certain
number of shallow donors. The fermi level (Ef) is 0.36 eV above Ei
(intrinsic energy level) at 300K. What is the donor concentration Nd?
For Si at 300K ni(intrinsic carrier concentration) = 1.5 x...
I have a few questions about this effect. If I have some semiconductor of N type in which I have electrical field in x direction, and magnetic field in z direction
\vec{E}=E\vec{e}_x
\vec{B}=B\vec{e}_z
Then Lorence force is in the -y direction because in N type of semiconductor n>>p so...
Homework Statement
I'm attempting to understand better how optical transitions occur in a QW (more specifically quantum cascade lasers) with and without an electric field.
If an electron in the second excited state falls to the first, is it simply the transistion matrix between these two...
Homework Statement
Hello, everyone! As a rookie here, I want to ask a question for help.
As for doped semiconductor, it is easy to find the answer based on the atom property. But for a intrinsic semicondutor, it seems hard to do so. I'd like to know what can be done to distinguish a n-type...
Hi guys,
I just have a few questions regarding semiconductors and p-n junctions.
How can I explain using an E vs k diagram why a silicon based device can be an efficient light detector but not an efficient light emitter? I imagine it has something to do with the fact that an electron in the...
Homework Statement
I'm trying to find energy level above Ec where electron distribution makes a peak for a nondegenerate semiconductor. For this case we may take GaAs having Eg = 1.42eV at T = 300K.
Homework Equations
m_e=single isotrophic effective mass or m_0
energy states, g_{c}(E) =...
Homework Statement
The resistance of a semiconductor decreases rapidly with increasing temperature. The main factor contributing to this effect is the rapid increase, with increasing temperature, of
a. the speed of the random motion of the free charge carriers
b. the concentration of the...
Hi, I have a super capacitor that is charged at 100,000+V at 0.1uF. Naturally it wants to give of its energy instantaneously in a spark; but I am trying to find a compound or semiconductor that can regulate the output of electricity from this capacitor without wasting the majority of the energy...
Hi Guys,
I'm not sure that this is the right place to ask for it, and the thread may be moved to another section, but do anyone have the solution manual of :
Semiconductor Devices Physics and Design not Physics and Technology
I am despratley trying to solve a homework that questions...
Eg) Silicon Material
When we say about mobility of a semiconductor - we basically have to consider its properties etc. One of it is impurities. Here we have to consider its TOTAL Dopant Concentration?
What is the difference between a solid state relay and a semiconductor contactor?
Can both switch ac loads? This a link to a company that distinguishes between the two.
http://library.abb.com/global/scot/scot209.nsf/veritydisplay/da7ec357f6a7461cc12573ad004e1e83/$File/2CDC110004C0205_07.pdf
I am curious about the operation principles of semiconductor lasers, but I never had the chance to go through the basic flow.
I'd be grateful if someone posts a brief description of how the light amplification is achieved in simple terms.
I'm looking for a way to get accurate opinions, experiences and recommendations from others in industry on the quality of different electronic suppliers. Specifically, I want to know the quality of the suppliers of MCUs.
What are your experiences with Freescale, Renasas, Microchip, Infineon...
hi folks, almost done my semester of physics. this problem has my goat, can't quite figure it out. Done web searches endlessly, but most of the links are pdf articles that I can't access.
Homework Statement
A donor electron moves in doped semiconductor, for which ε/ε0 = 17.9 and m* =...
hi I am doing my Electronics and Communication Engineering..I need a topic for paper presentation.Im more interested in semiconductor devices and device physics..It's like,i would like to address any physical limitation in the existing technology in reducing chip size.(this is the only topic i...
I read about the closing of GMT's semiconductor fab (that happened in 2001) because it was on the EPA's list of hazardous waste sites and that made me wonder, both historically and now what pollution has come from semiconductor fabrication?
Homework Statement
I have a question on semiconductor device,,
A drift current density of Jdrf=150 A/cm2 is required in a semiconductor device using n-type silicon with an applied electric field of E=25V/cm. Determine the imjpurit doping concentration that will achieve this specification...
Hi,
Ok, so let's say we have a non-degenerate n-type semiconductor such that the Fermi-level/chemical potential is somewhere in the bandgap (probably needs to be low temperature). Typically in a metal you would say that the Fermi velocity is \hbar k_F/m_e. But since the Fermi-energy is below...
You are given a piece of metal of one square cm area and 10cm long. You do not know whether it is a conductor or a semiconductor. Devise some experimental setup to know the nature of the material.
I'm working on some calculations on Al0.35Ga0.65As & In0.65Al0.45As.
Someone can tell me where i can find the elastic/piezoelectric/dielectric constants for these rare alloys?? A database for them exist for us to search??
Thx...
Couple of electricity questions here.
4. (a) Show that in a steady state, any isotropic material that obeys Ohm’s Law contains
no regions with net charge.
(b) In certain types of anisotropic materials, the conductivity is not a scalar but
instead a tensor that can be represented as a...
Hie. I would like to know anyone who knows or have idea on design static and dynamic model for Semiconductor Optical Amplifier? Currently my lecturer ask me to design using Optisystem software which I quit blur on designing this models. Anyone who knows and help me please.
Thanks in advanced..
Hi,
could you explain me
polarization dependence of SOA amplifiers.
and
how to transfer the transverse electric (TE) mode to transverse magnetic (TM) mode. Are there any passive components to do it?
I am a graduate student working in semiconductor physics. I have been asked to give a presentation to high school girls about my field. The problem I am running into is that the organizers would like me to provide something hands-on that the girls can do relating to semiconductors. I have not...
Homework Statement
This isn't a problem as such. This is about a practical I did, to verify the non-classical model of silicon conductivity (which increases with temperature) and then to calculate the band gap energy of silicon.
Homework Equations
This was the main equation of the model...
I'm wondering what determines Si indirect semiconductor?
Si is cubic diamond structure. So it's optically and electrically isotropic (1st&2nd rank tensor properties). And why is GaAs direct semiconducto even though its crystal structer and chemical bonding is so simliar to Si?
Isn't it crystal...
Homework Statement
For a forward biased P plus N abrupt junction diode, Lp = 1 micrometer, and at x = xn (x' = 0), the ratio of the hole current to the electron current, Ip/In, is 100 in the steady state. Determine Ip/In at x' = 1 micrometer.
Homework Equations
Jn = In/A
Jp = Ip/A...
i am not able to understand this line..
in semiconductor laser the transition probablity for a radiative transition across the conduction and valence gap must be high and must exceed the probablity for non -radiative transfer of energy to the lattice.
please explain this theory.
Homework Statement
I'm using Exciting software, which run in Linux for windows (virtual).
My task is to find band gap, energy gap and so on for semiconductor material using this software. I have to find band gap, energy gap and so on properties for Thallium Gallium Phosphide (TlGaP). To get...
Here's a story about a new proposal from Prof T P Ma, called Unipolar CMOS:
http://www.semiconductor.net/article/CA6602780.html?desc=topstory
This may take the P out of P-N semiconductors, boosting performance by 3 to 20 times, depending upon the material.