Band gap Definition and 85 Threads

I am new to solid state physics, having been in computational chemistry (quantum mechanics) for the larger part of my career. Hence have a lot of newbie like questions that are not easily answered by google/wikipedia searching. 1)In viewing a 1-dimensional band gap diagram, crossing the...

I'm reading a paper on photovoltaic hydrogen production and the author claims that for reasonable solar efficiencies the band gap must be less than 2.0eV. This I understand. My question is how will it effect the photon absorption if the band gap is much smaller. Say the band gap energy is...

Hello, do you know why no electron can stay in the band gap? Is it impossible at every energy? Thank you!

Might be an easy question (or not). What determines the band gap of an element? As far as I know, silicon is the most efficient single-element semiconductor because of it's small (but nonzero) bandgap. Next (as far as I know) is Selenium. I'm aware there are more efficient compounds, but...

I am reading about solid state electronics(semiconductors). I've read that when atoms of many many atoms are brought close each other,as in a solid, the energy levels of energy states of different atoms get split up into different closely lying energy states collectively forming a band...

Homework Statement Calculate Efi with respect to the center of the bandgap in silicon for t= 200, 400, 600 kelvin. Homework Equations ni = Nc e^-((Ec- Ef)/(kt)) k = boltzman constant t= temperature in kelvin Ec = energy level of the conduction band ef= fermi energy level ni=...

Hiya, been given this question which I am having problems with. Semi conductor quantum well structure contains a 100A thick layer of GaAs between thick AlGaAs layers. Find the band gap for the structure, where GaAs has the following parameters; conduction band effective mass 0.067 me, heavy...

The band gap discontinuity in DFT? Hi everybody... I've read about the band gap problem of Density functional theory, there is a discontinuity of the band gap when an electron add to the Kohn-Sham system I have two questions could anybody answer me? please 1- why this discontinuity happens...

I am not able to understand how a bandgap voltage reference works. The simplest ckt I found was here - (figure 2) - http://www.national.com/rap/Application/0,1570,24,00.html You have 2 branches of diodes, in one branch rich (high) current flows and in the other lean (small) current flows...

When we say generally TiO2 band gap energy, is it meaning direct or indirect band energy? Some papers show only direct BG or indirect BG or both. Is it right that one semiconductor has one of direct and indirect BG. I am a little bit confused.

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...

sorry i moved it to correct forum i rushed in, in my panic

indirect band gap semiconductor doubt its said that indirect band gap semiconductors like silicon and germanium are not used as a light sources because they have more non-radiative recombinations rather than radiative ,which inturn decreases efficiency of optical source. but i want to...

I was wondering that how the knowledge o transmittance and reflectance curves can give us information about the band gap and electronic structure of a metal? How these curve differ for semiconductors? I desperately tried to extract n, k values from the reflectance curve of a nitride material...

Hey I was studying for my test, in my notes it says si cannot be used for led, because it has indirect band gap.Why indrect band gap is not useful for led?

how the conduction band offset varies with Al concentration?? what is the different?

How does the band gap not violate the principle of least energy? Surely the most favourable states are those with minimum available energy - but there is a gap!

Hello all, I'm just getting to grips with conduction in solids and am trying to find some values for the band gap between the valence and the conduction bands. All I can find anywhere are typical values for semiconductors (or about an eV). I also found that carbon in the diamond configuration...

How does a direct band gap (like that in GaAs) vary with its well width?

band gap arises due to lattice potential.band gap is produced at zone boundary due to bragg reflection.there it behaves like standing wave instead of traveling wave?further formation of 2 standing waves?please help

Hi guys i have a question about how semiconductor materials absorb photons at less than the band gap energy. Particularly in an indirect material like silicon. Looking at absorption spectra for silicon i expected for it to immediately drop off at lower than the band gap energy ~1100 nm (1.12...

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...

Can a semiconductor absorb a higher energy photon than its Band gap Eg and make a transition from valence band to conduction band? For a example commonly used IR detector is InAs (semiconductor) whose Eg is 0.354 eV, if a blue light falls on it, will it able to absorve that energy and make a...

In the first diagram on http://hyperphysics.phy-astr.gsu.edu/hbase/solids/fermi.html" , the band gap in a semiconductor is shown. What is the corresponding Fermi momentum? If you plug E_F into the dispersion relation, you get no solution for k_F, right? I ask because an equation is given...

My physics/electronics teacher told me some thing really interesting and confusing a wile ago and I have been trying to get my head round it. The forward voltage in a LED (voltage needed to drive the current) is proportional to the band gap energy. However Blue LEDs have a higher forward...

hello to everyone. It is normally said that in semiconductors the Fermi level is half way between the valence and the conduction band. I have the following question on that: what does it mean that the Fermi level is in the band gap? It should mean that the maximum energy of an electron in the...

i know this is a simple question, but i have been looking for a while (maybe 15 min) and i cannot find what is so special about Cu, Ag, and Au? i know there is something special about these 3 metals. something that none of the other metals have. i remember it having to do with fermi velocity /...

Glass is transparent to visibile light under normal conditions; however, at extremely high intensities, glass will absorb most of the light incident upon it. This works through a process known as multiphoton absorption. In this process, several photons are absorbed at the same time. If very...

Homework Statement [Edit: Please also see additional posts below. I have tried to clarify my question somewhat but didn't want to edit this one just incase anyone can help with the full problem. Thanks! :) ] I did a lab on the band gap in germanium where I measured the voltage across a...

Question: A light-emitting diode (LED) made of the semiconductor GaAsP gives off red light \lambda =650nm. what is the band gap for this semiconductor? I know the E=hc/ \lambda so it means the band gap is 1240/650=1.9 ev ??

what does "band gap bowing" means? Hi, i speak spanish, and I've tried to translate the term "band gap bowing", but literally it doesn't have any sense. So, can anyone explain this term to me so i can translate it correctly?? Thanks a lot.

I am looking to calculate the energy gap of for starters periodic elements and were wondering how we could get the list and calculation. Is there a table somewhere based on certain temperatures and constants of energy gap level? We would like to get a list of the energy gap energy for valance...

Would anybody be able to provide me with data concerning the band gap of colloidal CdSe quantum dots against their size?? I am currently using CdSe dots with a ZnS shell, capped with HDA. Any relevant information would be much appreciated. Many thanks, David Cunnah (studying PhD in opto...

Hi all, We say the energy difference between the Top of Valence band and the bottom of Conduction band as the forbidden gap or Band gap. But when we see the fermi level at zero Kelvin, its exactly at the middle of the band gap. Does this mean that there is possibility for an electron to...

Hello, I am in the middle of revising topics for the materials section of myend of year exam. For some reason my department give out past papers but do not give out answers. Any answers to any of the follwing questions would be very helpful. I don't think too much detail is required just a...