Semiconductors Definition and 206 Threads

Aasslam u alaikum to all, i have confusion in knowing that " how fermi level form in a compound semiconductors e.g GaN, GaAs, etc. Thanks to all

When using k.p theory to calculate the magnitude of the electric dipole moment in semiconductors for band-to-band transitions, the value of the dipole moment is basically fitted to the effective mass of the electron in the conduction band. However, the values turn out to be larger than the...

Hi all, I've calculated the exciton binding energies for different semiconductors using the Bohr model. It works remarkably well for direct gap semiconductors, but it is not good for indirect gap semiconductors (in Si and Ge, there is an underestimation by a factor of 3, approximatively)...

i read in an online course about semiconductors that electric field between E_c and E_v given by: E=\frac{dE_c}{q dx} and i know the general form of electric field is : E=\frac{k.q_0.q}{r^2} and what is the direction of this field ,i know from positive to negative , from E_c to E_v...

If we have two semiconducting materials say silicon and germanium and in this specific case silicon has a very large donor area energy say 25Mev and a very small energy gap, say 1.1Mev and germanium has a smaller energy gap then silicon, 0.6Mev and a donor energy of 2Mev. I amtrying to figure...

Homework Statement I've been given some Bench Notes for a Physics experiment I am supposed to be writing a report up for. What the notes show is a graph of logp (log of resistivity) and logn (log of number density of charge carriers) for given N and P type semiconductors. What is clearly...

Hi Strictly from the definition of the Fermi level as the highest energy occupied at zero temperature, it seems that in the presence of a band gap the Fermi level (Ef) could be placed fairly arbitrarily anywhere between the conduction (Ec) and valence (Ev) bands, since the density of states is...

are semiconductors charged? i mean '"n" type contains excess of electrons, so they should be charged... please tell me where i am wrong tks for any answer...

if we have a molecule or atom then if we take avogadros number amount of this unit then the amount will weight the atomic mass in grams. \rho _m/A rho is the density A is the atomic mass why their dinviding gives us moles per cube cantimeter ??

Qs: How "Group" and "Period" affect semiconductors Background: I have a BS in CompSci, not Physics, so if this question stuns you in its naivete, please forgive me. In the last couple weeks, I have been reading up on PN junctions and how they work. I've also seen the standard Si/Ge (Group IV) +...

Homework Statement Here is an excerpt from a work Homework Equations The Attempt at a Solution What I don't understand is the excerpt. Okay, silicon is #14, which has 3s2 3p2, total of 4 valence electrons. But I do not know (1) first, which and where is this surplus electron referring...

Can some1 please assist me with this question,i have tried every means possible with no avail. 1, A wafer of intrinsic silicon is deliberately doped with 3 X 10^20/m^-3 of acceptor atoms 1, CAlculate the electron and hole concntration in the wafer 2,calc the position of the Fermi level in...

Hi, I was just doing some reading on semiconductors mostly with respect to photovoltaic cells. I understand that doping silicon with Boron and Phosphorus creates a good semiconductor because the extra electrons from the phosphorus jump over to the 'holes' provided by boron, and then creating...

I would request for help in understanding why the drift speed of electrons in semiconductors is more than that of holes. Thanks.

That's my question: how can I tell, from the molecular form of the compound, if a compound is an intrinsic semiconductor, an extrinsic type-N semiconductor, or an extrinsic type-P semiconductor? I can tell the pure intrinsic semiconductors: Si, Ge, C (diamond), etc. I know that if I add an...

Hello everyone, I have a (simple?) question: How do you differentiate a material to be a conductor or a semiconductor? It is just only by examining the material's electrical resistivity/conductivity whether it is low or high? Because I have heard that even some metallic conductors have high...

Hello everyone, I have a (simple?) question: How do you differentiate a material to be a conductor or a semiconductor? It is just only by examining the material's electrical resistivity/conductivity whether it is low or high? Because I have heard that even some metallic conductors have high...

Hi all It can be shown that the product of the hole and electron concentration is constant at a given temperature in a semiconductor, as long as the Fermi level is in the ~middle of the gab. When we dope semiconductors, do we use the above argument? I.e., does doping work because of this...

A piece of Semiconductor is irradiated by light, will the light effects on resistivity be intensified or reduced if the temprature is increased? why?

Hallo, Please help me ASAP. I need to know approximate value for Kane Energy(Ep) of GaAs for calculations of oscillator strength. Thank you!

if we heat semiconductors, so that the energy provided is more than threshold energy will they generate a current?

Addition of pentavalent impurities to Si will result in each dopant forming bonds with 4 si atoms and, so 1 atom of the dopant will be left out. On adding a trivalent impurity, the dopant will form a bonds with 3 Si atoms...so how does an electron disappear to make a hole? Why does the...

Hi, I would like to know how we can use indirect band semiconductors in lasers. Such type of semiconductors do not emit photons when transition takes place. Energy is given up as heat to the lattice. Regards,

Although photomultpliers are the most sensitive light detectors, are there any other radiation counters that utilize photo-transistors, or other means, to detect photons emitted form a scintillation crystal when hit by incoming radiation?

Hallo Is there someone that can explain why Al can be used to form Ohmic contats to both p- and n-type Si? When looking at a Ohmic junction between a metal and a semiconductor, it is formed when the work functions are as follows: \Phi_m>\Phi_p and \Phi_m<\Phi_n. How can Al fulfil both or...

A semiconductor material has an intrinsic carrier concentration of 5.6 x 10^14 m^-3 at 300K. What is the electron concentration when such a semiconductor is p doped with an acceptor concentration Na = 3.9 x 10^18 m-3. I have no idea how to approach this question without a value for the...

The ohm law for electricity is given by R = V/I Yesterday, my friend just took an experiment report to me which show the relation between R, V and I on a resistor and semiconductor separately. I saw that for resistor, R is almost a constant so V vs I is a straight line. However, for...

Hi everyone, Recently I am working with a research which involves some semiconductors. In the basic level, semiconductor can be classified as intrinsic (undoped) and extrinsic (doped) semiconductor. Then extrinsic semiconductor can be divided into n-type and p-type. For example, the below...

I was taught this in school but my teacher could not explain why the band splits again with decreasing atomic distance. Also, then i wondered how do you explain the fact the it splits again nicely into 4N states for the valence band and 4N states for the conduction band? Could some one help...

Can anyone tell me what is the "Brus Approximation" in case of the bang gap of semiconductors?:rolleyes:

Homework Statement I'm trying to understand this part of my notes where the optical absorption in both indirect and direct bandgap semiconductors. This part specifically mathematically describes the change in energy and momentum of an electron in a semiconductor after it has absorbed energy...

I understand that holes are sites of missing electrons in the structure of a solid semiconductor. When there is a potential difference between the ends of a sample, electrons can move to fill the holes and in effect the holes move the other way to form an electric current. However, is the...

[SOLVED] Optical absorption in Semiconductors Homework Statement I'm doing a lab report on the optical absorption of semiconductors. More specifically it was to determine the bandgap values of the semiconductor samples. This is the experimental setup...

I am reading 'Mesoscopic electronics in Solid State Nanostructures', second edition, by Thomas Heinzel. And I find it a bit too difficult from time to time. Especielly on the concept of Fermi level pinning in doped semiconductors. Does anyone know where to find a good explanation for this...

Which groups in the periodic system forms compounded semiconductors? Is it those who can share 8 valenceelectron together? or is it those who can share 4 valence electrons together? If this is the case why is it just those who can form compound semiconductors? Can i use the...

The lasers used to "read" CDs, DVDs, and Blu-ray discs operate at 780 nm, 650 nm, and 405 nm, respectively. These are produced through semiconductors. Find the energy gap needed for each laser. (Blue-ray discs can have higher information density because of the shorter wavelength). Ok. I...

Ok, so in an intrinsic semiconductor we know that the intrinsic concentration ( n_i ) is roughly 10^10 cm^{-3} at room temperature, and that n=p=n_i under equilibrium conditions. Now why is it that at zero temperature, (i.e. 0K ) does n_i have any value? I know that that n_i does...

For metals, work function is defined as the energy gap from fermi level to the vacuum level and electrons can escape from material if they have a certain mount of kinetic energy that is larger than the work function. But, how can we define the work function for the semiconductor or it is totally...

If cost wasn't an issue, what would semiconductors be made from to maximise their efficiency,useful lifetime etc?

I understand the principle behind p and n type doping, but I don't understand how such a small amount, 1ppm, can cause such a massive change in the fermi energy. as I understand it: for the intrinsic case the number of electrons exactly matches the number of holes and the fermi energy...

URGENT x 10 DERIVE a 6x6 Hamiltonian for bulk semiconductors Okay here is a little challenge for you guys. Try and test your skill a little. First 10 people to properly derive a 6x6 Hamiltonian for bulk semiconductors will gain bragging rights in this forum.

in books we have read that there lies a forbidden gap between conduction band and valence band. and electrons can not exist in this gap i.e. probability of electron being found in this region should be zero. BUT the fermi level,which has 50% prabality to contain an electron is found in...

I've posted a similar question to the high energy forum. As I understand it, LEDs emit photons when electrons and holes have sufficient energy to cross a particular "well". I'm sure this explanation is lacking in many key ways. Why can't we "tune" the gap to create electron-positron pairs and...

Hi, I am trying to get a feel for electrons in semiconductros (say GaAs) with regards to the bandstructure of the material. I understand that the velocity of the electron can be written as ~ d(Energy)/d(wavevector) so at band extrema such as Gamma-point or X-point this goes to zero...

Can someone explain the difference between an intrinsic, extrinsic and nonstocichiometric semiconductor?

Hi guys. Could someone please explain to me this electron hole theory that people use to describe the behavior of electrons inside semiconductors? How do these holes move, in and out of a potential difference? Thanks guys.

this question was in my material science exam . by the way I'm not very good at this subject

Hello everyone. Does anyone know of a good book that explains semiconductors? I specifically need to know about band theory and how semiconductors work. I am giving a talk in two weeks and want to really know my stuff. I'm willing to spend a lot of time to learn this stuff well. Can anyone...

Anyone have any good references or insights on excitons; excitons in bilayer semiconductors; excitons in high magnetic fields (fractional quantum Hall regime) or Bose condensation of excitons ? I'm going through the literature but want to make sure there isn't something useful out there that...

Validity of hydrogen model for Diamond semiconductors Hi I've calculated the shallow impurity binding energy for diamond for an experiment I'm doing.. I'm just wondering how valid is hydrogen model for this? We assume that the free electron and donar nucleus can be modeled as a...