Semiconductors Definition and 206 Threads

Hello! In order to obtain the number of actual electrons in the conduction band or in a range of energies, two functions are needed: 1) the density of states for electrons in conduction band, that is the function g_c(E); 2) the Fermi probability distribution f(E) for the material at its...

Hi! When dealing with a pn homojunction, it is easy to see the features it has at equilibrium, and also the features it has with forward/reverse bias. Plots show the constant Fermi level at equilibrium and the different Fermi levels for a forward bias; moreover, examples show how much the bands...

Hello! The (potential) energy of an electron in a solid structure is always negative; also the E_c and E_v levels (conduction band and valence band limits) are negative, in the band diagram of a pn junction. When the junction is built and thermal equilibrium is reached, the depletion region...

Hi all, new poster here, I graduated First Class with a BS and an MS, specialisation Electronics, from Calcutta University, scoring University highest grades in my special paper, Electronics. Since then, for the past 15 years, I have been teaching at various schools, colleges, and currently an...

How can i calculate this plot (photon energy dependence of the optical gain (or loss = negative gain) of GaAs with the injected carrier density as a parameter? Show calculated plot based on this equation Given parameter: mc=0.067 me; (effective mass of electrons in conduction band) mv=0.48...

Hello! Some of the processes caused by a pn junction are not clear for me. Just after the contact between the p and the n region, a migration of charges happens in a semiconductor junction in order to reach an equilibrium condition. A valence band and a conduction band are present in both...

Hi, Lately, I've been trying to compare and understand conduction properties of metals and semiconductors. However, there are two question on my mind that I'm still trying to figure out. Maybe someone here might be able to provide some clues. 1. It is known that a linear increase of the...

What would happen if in reverse bias of a pn junction diode voltage greater than/equal to breakdown voltage is applied? Consider a zener diode with breakdown voltage 3V(just take as example).If we directly connect it with a voltage supply of 4V what would happen?I read that voltage across zener...

Hello Forum, An electric current is the flow of electric charge: charge in motion. The charges can be electrons, ions, etc. movingi in a solid, liquid, gas. When dealing with semiconductors the concept of hole is introduced. I understand that only the electrons are moving and the constitute...

I have big trouble understanding how current flows in semiconductors. As i have understood it it has to do with "valence" and "conduction" bands. I see valence bands as an discrete energy level within an atom that are possessed by electrons. These electrons do not contribute to a net current...

Hi, I'm a retired (since 2011) Physics prof from the University of British Columbia. I originally set out to get a PhD in Physics to increase my credibility as a science fiction writer, but I discovered a field* that was so cool it was like being a character in my own SF novel. In short, I got...

Why is the conduction band state s-type and the corresponding valence band state p-type?

Do I understand it correctly that photoluminescence at a semiconductor heterojunction occurs because of intralayer recombination? If so, why can't photoluminescence occur because of interlayer recombination? Is it because momentum cannot be conserved in such a process ( like in the indirect gap...

Can anybody explain my what is the origin of this forbidden gap? I mean how it was created and what is the physics behind this issue?

I'm looking to find out what is degenerating in a semiconductor that is being bombarded with beta particles. I know in the low energy tritium beta cells. There is less degeneration because less energy. I know that current is formed by the beta particle making pair holes in the mobile band. Is...

I was motivated to research this by discovering plans for a Venus rover: Windsurfing on a Wicked World | NASA That planet has the problem of a surface temperature of about 450 C and pressure around 92 bar. Its atmosphere is mostly CO2 with a few percent N2 and much less of various other gases...

Homework Statement (a) Find energies of states at ##(\frac{\pi}{a},0)##. (b) Find secular equation Homework EquationsThe Attempt at a Solution Part(a)[/B] In 1D, the secular equation for energy is: E = \epsilon_0 \pm \left| V(x,y) \right| When represented in complex notation, the potential...

Homework Statement "The low [electron] density of a semiconductor means that the conduction electrons travel much faster than they do in conductors." In order to fully understand this, I feel that I need to know why this occurs. Homework Equations I = nAve Where: I = current n = electron...

Here are some of my thoughts: - thermal management of individual LEDs in a RBG system - photon absorption in phosphor coating - exponential decay in intensity - CCT/ CRT?

Hello. I'm currently taking a physics course that gives me the freedom to take any subject related to semiconductors and do some research on it, presenting it at the end of the semester. I know I want to do something related to programming, but I'm having a hard time finding a theme. Hence me...

Homework Statement Show that the minimum conductivity of a semiconductor occurs when n0 = ni√(μh/μe) Derive an equation for the minimum conductivity Calculate the (i) minimum and (ii) intrinsic conductivity for silicon. State the assumptions you make and the origin of any material properties...

why the solution for energy levels of electron in 1D crystal lattice as solved in Kronig penny model has used wave vector k differently then the Schrödinger equation solved for a free particle. (only the conditions in the equation has changed not the maths...so the "USE" of wavevector 'k' must...

I understand the difference between p-type and n-type semiconductors but I just don't understand how adding a p-n junction to a circuit affects it. Can someone please explain how semiconductors work? For example, if I had a circuit with just a battery and a light bulb, what would change if I...

So I was reading about magnetic semiconductors and I got confused so can you please clarify I will ask a question that is made up of two parts. Magnetic semiconductors are ... a) devices that alter or switch on/off electric current flow depending on the magnetic field strength etc applied OR b)...

Hi. Specifically I would be interested in a not-too-advanced book (I don't know Quantum Mechanics) on semiconductor physics. Specifically, point defects and photoexcitation effects on semiconductor properties, energy levels, etc. Am I asking for too much?

Hi I am looking at the problem of optical absorption in direct gap semiconductors. It seems like the perturbing Hamiltonian is an oscillating perturbation , ie. an electromagnetic wave. Why can't the problem be treated as the absorption of a single particle , ie. a photon ?

So, recently I started learning about electronic components and then I started learning about semiconductors. The one which I've been having some real trouble to understand its function is the transistor. So I bought an electronics textbook called El ABC de La Electrónica (The ABC of Electronics...

Homework Statement http://postimg.org/image/hf6zpmykr/ Homework Equations intrinsic carrier density = ni = 10^10/cm^3 (for Si at 300K) The Attempt at a Solution Its a really elementary problem but I can't figure out the difference between some quantities. For example, free electrons and holes...

A structure with free electron density around 10^26 m^-3 is considered as a highly doped semiconductor or a metal? Or in other words, what is the lowest possible free electron concentration for a metal and what is the highest possible free electron concentration for a doped semiconductor?

I don't understand the concept for polar and non-polar semiconductors, generally speaking about propagation of existence of phonons (acustic or optics). Thanks. I don't find any thread about this concepts.

I am learning the basic make-up of LED's and they mentioned conduction and valence bands. What I am unsure of is which of these bands are either the p-type or n-type materials within the LED/semiconductor, and/or which band is positive with holes or negative with the free electrons. Can I just...

I'm very new to semiconductors. I want to do basic calculations. How would I go about calculating and graphing the energy of the electrons and holes given the magnetic field and the state. Also, how would I do the same for the electron and hole population.

valence band and conduction band overlap in conductors but not in semiconductors and insulators why?t

I've been doing a bit of reading on bandgaps of semiconductors and alloys of semiconductors. I was curious to know is the bandgap of a material, say Silicon, determined or calculated experimentally? How do scientists usually determine this in the lab?

Hello Integral and all the forum members, Before approximate 8 months I read that some big companies begin to invest a lot of money in change the wafer size from 300 millimeters diameter to 450 millimeters diameter, in these days one friend tell me that he hear that all the industries in...

My base understanding of the solar cell is as follows: Light hits metal in solar cell and emits electron via photoelectric effect. There is n-type silicon which has an overall negative charge due to excess electrons. There is also p-type silicon which has an overall positive charge due to a...

When studying about semiconductos what are the valence band and conductivity band .what are its properties,where is it addressed.

How is it that certain electronic goods are designed to fail? Planned Obsolescence is just that, planned. So what goes into designing failing systems of computer? Hypothesis: Perhaps there are defects in the n and p-type doped semiconductors. The lattice entropy increases over time producing...

I've known that the conductivity of semiconductors increase with temperature because more electrons are freed, But why doesn't the scattering and vibrations of the lattice affect the conductivity in semiconductors as in metals?

Hi, Could any kine soul please explain this to me: I know that diffusion is movement of impurities (dopants) into the semiconductor especially happening during heat cycles in fabrication process. but what is the dopant redistribution? Is it movement of impurities toward the surface? Thanks in...

Hey guys I've got an assignment. I need a comparison between a normal conductor and a semiconductor and why a classical understanding isn't enough to explain how an SC works. Also are there any electrical properties of an SC besides decreasing resisitivity at higher temps?

there are two type of charge carrier in semiconductor , one is electron which carry negative charge and other is hole which carry negative charge , electron meet with hole and they recombine , Q1 what is carrier transport Q2 what is carrier statistics in semiconductor

Homework Statement It's the third part which I'm stuck on. Homework Equations The Attempt at a Solution I've substituted in all the numbers and, multiplied by the density but I am still not getting the correct answer; where a I going wrong? I got 6.13*(10^11) m^-3 The answer given is...

Consider a long semiconductor bar is doped uniformly with donor atoms so that the concentration is given by n = ND and is independent of position. Radiation falls upon the end of the bar at x=0, this light generates electron-hole pairs at x=0. light keeps on falling. Explanation...

From thermodynamics we have dU=Tds-Pdv+\mu dN. So the chemical potential is the energy change due to adding an extra particle when S and V are constant. Now consider an intrinsic semiconductor at T=0 in which the valence band is all-occupied and conduction band is empty. If we add an extra...

Edit: I've made some progress on this one, and I now understand that the valence and conductance bands are composed of molecular orbitals contributed by each metallic atom joining the molecule. For example, three lithium atoms would contribute three total molecular orbitals, resulting in three...

Consider the Sommerfeld-model of a metal. We have a discrete but very large number of possible states, bounded by the Fermi energy. Since the distance between the levels in a potential well scales as 1/L^2, for a very small specimen the number of states becomes small as well. Taking the...

I am reading Analysis and Design of Analog ICs by Gray and Meyer. In Ch. 2, they describe using MOS technology for fabricating on-chip capacitors. First and foremost, what exactly does surface potential mean in the context of semiconductors? Quoted from Gray and Meyer (5e), Page 149...

Which mechanism in semiconductors is responsible for electron excitation from valence to conduction band in thermal equilibrium at temperature T? Do valence electrons take their excitation energy from the lattice by absorbing phonon? If so, they can be excited at each arbitrary temperature no...

where are the holes in the p-type semiconductor situated? in the conduction band or the valence band? i am talking about the holes formed because of the acceptor impurities, not the thermally generated ones.