Semiconductors Definition and 195 Threads

I have searched a lot on the internet for a simple explanation of these two terms. As I have understood these things (quantum physics), after reading from a lot of sources, is that in an atom there are discrete energy levels and electrons occupy the levels according to the least energy of the...

I had a problem understanding the hall effect for flow of holes... I thought flowing of holes means that the electrons are flowing the opposite direction,leaving open holes and that's it... but when reading hall effect I couldn't explain the hall effect for electrons and holes... Suppose holes...

Why does the Fermi level level drop with increase in temperature for a n type semiconductor.? What's the basic idea behind Fermi level? How does it get affected by temprature?

How can the mass of a hole is larger than an electron?I want to know what a hole signifies and the mass energy required for it to propagate in the semiconductors for constituting current.

Dear Physics forum users The below figure is from http://pubs.acs.org/doi/full/10.1021/jp0009305 In Fig. 3, energy band diagrams are shown for a semiconducting material inbetween two metal electrodes. The figure caption is: "Figure 3 Energy band diagrams for (a) p-type SiNW (b)...

Is it because at high temperatures quasi-all electrons due to the doping are in the conduction band such that only the intrinsic behaviour is left? Or is it something else?

I am currently taking up a course in electronic devices and circuits. Our first topic was about semiconductors and I'm having trouble understanding the doping process. We didn't have any prerequisite solid state course or any other course related to it that's why my professor explains the...

Hi all, In a compensated n-type semiconductor where there are both acceptors and donors in similar densities, the acceptors are filled with electrons (and therefore have a negative charge) even at very low temperature, close to 0 K. Where do they get these electrons from ? Whether...

When electrons from N region diffuse to P region, the electrons combine with holes to form a -ve negative ion leaving behind a +ve ion in P region.So, my doubt is how the holes accept the electrons and get a negative charge because as the holes are positively charged, when they accept the...

Hello, I just watched this video, where Dr Brattain talk about semiconductor physics and I thought about what I learned in my solid state physics course, namely band theory. I have several questions : 1)The explanation in terms of chemical bonds given by Dr Brattain (around 10mins) seems a...

Homework Statement Design a solar cell, designed to absorb solar light. Treat the sun as a blockbody source of T=5800K. To design the cell, you may grow 4 very thin semiconductors of the following bandgaps, in eV: 1.43, 1.14, 1.35, 0.67, 1.75, 2.4, 2.7, 0.42, 3.37 Which of these would you...

Energy gap dependence on temperature for intristic semiconductors (Si,Ge) I need help on this topic, where to find text about this, and models that describe it (Varshni's model, linear model,...)

Homework Statement "A GaAs device is doped with a donor concentration of 3x10^15 cm^-3.For the device to operate properly, the intrinsic carrier concentration must remain less than 5% of the total electron concentration. What is the maximum temperature that the device can operate?"Homework...

in any junction diode or transistor...i don't understand the difference between minority charge carriers, majority charge carriers and the immobile charges that you see in the depletion region ..please explain??

Hi everybody. I'm new here and, first of all, sorry for my bad english :-D I'm studying photoelectric absorption in semiconductors. The book (and professor too) says that, in the conservation law: ki + kph = kf (where ki and kf are wave vectors of initial and final electron state, and...

Homework Statement Revered Members, When we increase the temperature, resistance increases in conductors. But resistance decreases in semiconductors. Why? Help in this regard will be highly appreciated. Homework Equations The Attempt at a Solution Due to increase in temperature...

Are there any other atomic elements that are capable for doping apart from the trivalent and pentavalent atoms? If any why is it not preferred over boron and arsenic?

I have a very poor understanding of how an electron "actually exists" in a crystal -- how it can be visualized. So conduction band electrons are supposed to be plane waves modulated by a periodic wavefunction (my understanding of Bloch theorem). This means they're basically everywhere in the...

Semiconductors -- role of displaced Silicon or Germanium Revered Members, When we dope a pure Germanium or Silicon with pentavalent impurity or trivalent impurity, the dopant replaces Silicon or Germanium and bonds with neighbouring Si or Ge atom. That is Dopant takes the centre position and...

How to sketch the band diagram of intrinsic semiconductors including the fermi level with the electric field present verses distance? Its not a homework question.

Ok, maybe someone can point me in the right direction ...hopefully anyway. I know this is probably a really stupid question, but as Mr Mackey in South Park said - "there are no stupid questions, just stupid people", so here it is. I was in class simulating N and P type CMOS devices using...

We have an experiment on Hall Effect,in which we place a semiconductor material in the middle of a 2 poles of a magnet exactly in the middle so that a distance of 1 cm exists between the poles. Questions: 1.Why is a semiconductor placed?Will it make any difference with a metal? 2.Why a 1 cm...

1. Fermi level is also defined as highest energy level at which electron can exist at 0K then it should be top of valence band but why is it in between conduction band and valence band ( in forbidden gap)? It should be in conduction band or valence band. How to explain this? 2. If density of...

I know holes are made/present after electron leaves its place but are holes present in metals during photo electric effects? what is the mass of a hole (if it has any)? what are its characteristics are they exactly opposite of electron ( i mean its behaviour in electric and magnetic field ) ?

Fermi level in an extrinsic semiconductor(after attaining thermal equilibrium) is said to be invariant (constant ) , and the proof uses the fact 'no current must flow thorough any cross-section'..But I don't think its true, charge will be transported due to diffusion and this is countered by...

When a n-type semiconductor is brought into contact with a metal, then alignment of the chemical potentials of both systems leads to band bending within the depletion layer, e.g on the semiconductor side. does the amount of band bending (change of potential) also depend on the donor...

This is something that has popped into my head recently. afaik, vacuum tubes were once the most common device used for switching, and amplifying. Then transistors and other semiconductor devices come along and almost wiped out vacuum tubes (not totally i think) what I want to ask is...

I have taken several courses in semiconductors at the undergraduate level. Both the pure physics part (k vectors) and the more engineering parts (silicon processing, band diagrams) etc. So for all the junctions (Schottky, Ohmic, p-n) - I have never managed to imagine the idea of the Fermi...

1.What happens to the electrical resistance of conductors, semiconductors, with increase in temperature? And explain why?

ok let's say i have a semiconductor like germanium with band gap of around 0.67eV at rtp. so this means that i need around 0.67 x 10-19 J of energy to cause valence electrons to jump to conduction band right? do i use the formula E = 1/2 kT to relate this energy to temperature? so i...

I would like to ask about the reason why the electron "effective mass" was introduced in semiconductors. What is its' usefulness ? And also about the so-called "effective mass theory" used to calculate energies for the shallow defects in semiconducors. What are mean pecularities and...

We usually plot the energy versus k, the wave vector, in the so-called "energy band diagram" for semiconductors. I am trying to understand the significance of "k" in this case. k is the wave vector, which means come kind of reciprocal of the space wavelength of the wave. But this definition...

how can we understand it please ? Thanks.

hi, can someone explain me what the charge neutrality level is in semiconductors. In particular, how do you define it with respect to the Fermi level? What about the Fermi level pinning? Is the branch point energy same as the charge neutrality level? How are these things related? I...

As I understand it, an exciton is created when an electron is liberated from the valence band of a semiconductor, but becomes bound to the hole that it leaves vacant via Coulomb attraction. We can calculate the quantized energy levels of the exciton just like hydrogen. I have done this for the...

Hi, i am doing a project course in masters. i need help regarding on X-ray Spectrum absorption by semiconductors. I am doing the simulations in XOP(X-ray oriented programs) software which is freeware at http://www.esrf.eu/UsersAndScience/Experiments/TBS/SciSoft/xop2.3 . So, my doubt is...

Hello, In my book it says that semiconductors have a full valence band and a fermi energy somewhere in between that valence band and the conduction band. But its two examples of semiconductors, crystals of Silicon or Germanium, have a 3s^2 3p^2 resp. 4s^2 4p^2 outer shell, so surely they...

Hi why is band gap indirect in semiconductors like Si ?and direct in semiconductors like GaAs?

please explain abt amorphous and organic semiconductors...their properties ...nature of classification ...examples..etc..

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...