Gap Definition and 288 Threads

Gallium phosphide (GaP), a phosphide of gallium, is a compound semiconductor material with an indirect band gap of 2.24 eV at room temperature. Impure polycrystalline material has the appearance of pale orange or grayish pieces. Undoped single crystals are orange, but strongly doped wafers appear darker due to free-carrier absorption. It is odorless and insoluble in water.
GaP has a microhardness of 9450 N/mm2, a Debye temperature of 446 K (173 °C), and a thermal expansion coefficient of 5.3 ×10−6 K−1 at room temperature. Sulfur, silicon or tellurium are used as dopants to produce n-type semiconductors. Zinc is used as a dopant for the p-type semiconductor.
Gallium phosphide has applications in optical systems. Its static dielectric constant is 11.1 at room temperature. Its refractive index varies between ~3.2 and 5.0 across the visible range, which is higher than in most other semiconducting materials.

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  1. P

    What is the value of the band gap in a good conductor

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

    How to Find Subgroups of Index 2?

    Is anybody familiar with this program? Better yet, can someone explain to me how to find subgroups of index 2 (or index a power of 2)? Thanks.
  3. H

    Reducing Gap Around IC Chip Pins for 0.5mm Track

    Hello, I am currently working on a PCB design project, just wondering if anybody knows how to reduce the size of the gap(the black circular region) around individual pin of IC Chips (after I have done the polygon pour) so that a 0.5mm ground track can get through. In addition, what is the...
  4. M

    Indirect band gap semiconductor doubt

    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...
  5. E

    Advice for Senior Physics/Math Major Planning a Gap Year

    I am a senior Physics/Math major. I want to go to grad school (99% sure) but I am not ready to start immediately after undergrad, I hope to bike to and live in South America next year. My question is, how harmful will this be to my chances at getting into a top tier physics Pd.D. program the...
  6. M

    Is it possible for electricity to jump a vacuum gap?

    Is it possible for electricity to jump a vacuum gap? If so, what is it called when that happens?
  7. H

    Understanding mass gap in Yang-Mills theory

    Here and there some rumors come out about this relevant problem. I have read the following article in Wikipedia http://en.wikipedia.org/wiki/Yang–Mills_existence_and_mass_gap and the talk page http://en.wikipedia.org/wiki/Talk:Yang–Mills_existence_and_mass_gap but people cited there...
  8. C

    BRS: Exploring the Rubik Group with GAP

    I. Introduction With great sadness I note the passing of one of the Best Things Ever: a few days ago, John Baez posted the final installment (Week 300) in his long-running internet column, This Week's Finds in Mathematical Physics. But John himself is not sad; he is desperate--- to...
  9. T

    Bohr's model applied to Wannier exciton in indirect gap semiconductors

    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)...
  10. S

    Toroid Air Gap: MMF, B-H Curve, Flux Density & More

    Homework Statement (I have done parts i) through v) correctly. It is the remaining two I'm stuck on. A toroid of rectangular cross-section has a height of 10mm, an inner diameter of 68mm and an outer diameter of 82mm. It is made of iron and is wound with 118 closely-spaced turns. When a...
  11. magnetic flux

    How to stay in touch with physics in a gap year?

    Hello, I just finished school and I want to study physics, but I have to wait about 1.5 years until I can start with it. What would you recommend to stay in touch with physics during that time? Reading books would be the thing I came up with, would you say that reading in forums like this...
  12. S

    Magnetic field through ferrous material and across air gap

    I am attempting to determine how strong a magnetic field will be on the other side of a thick material and then across an air gap. For instance, I have a closed steel cylinder with a steel piston inside it. I plan to affix a permanent magnet to one side of the piston (inside the cylinder)...
  13. R

    Transmittance, Reflectivity and Band gap

    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...
  14. O

    Why not indirect band gap for led

    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?
  15. M

    Gapless Excitation: Exploring Spin Gap Opening

    Hi Can somebody explain what is a "gapless excitation"? If it is an excitation, why does it require no energy (gapless) to excite the system? Thanks, Mavi
  16. F

    Lorentz Force in Magnetic Circuit Air Gap

    http://en.wikipedia.org/wiki/File:Magnetischer_Kreis.svg The attached image shows a magnetic circuit with a small air gap. The magnetic material on each side of the gap is attracted to the other side. I've seen the magnitude of the force calculated based on principle of virtual work...
  17. D

    Understanding AlGaAs/GaAs Band Gap and Conduction Band Offset Variations

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

    Mass Gap Solved: New Theory May Address Claymath Problem

    If I am not mistaken the problem of the mass gap in in QYM, is a claymath problem, if the author of the next blog has proven it, shouldn't his article make more background noise, i.e be noticed by the media? Here's the link: http://marcofrasca.wordpress.com/?s=mass+gap Or he hasn't proven...
  19. C

    BRS: Subgroup lattice of a Permutation Group via GAP

    I am somewhat distracted so this post will not be what it should, given that GAP is one of my interests. For those who don't already know: GAP is a powerful open source software package for computational algebra, especially computational group theory and allied subjects. This long running...
  20. M

    Band gap - violation of principle of least energy?

    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!
  21. D

    Could a Billion-Year Technology Gap Exist?

    Interesting article... http://www.dailygalaxy.com/my_weblog/2009/11/the-billionyear-technology-gap-could-one-exist-the-weekend-feature.html?utm_source=feedburner"
  22. H

    Energy Gap of Electron in Dirac Comb Potential

    Pg 202 of Griffiths Introduction to Quantum Mechanics Homework Statement Hi, I am trying to solve a question involving band structure of solids... The electron is placed in an area filled with positive ions which is represented by a dirac delta potential... Homework Equations The...
  23. A

    Gap after MSc in Astronomy, will it hinder my chances of getting a PhD position?

    gap after MSc in Astronomy, will it hinder my chances of getting a PhD position?? hi all, I am an Indian student and I got my BSc in physics (Distinction) in 2006 followed by an MSc from UK in Astronomy (Merit) in 2007 (one year). I did not apply for a phd after my MSc as i thought that...
  24. M

    A 29-Year-Old Seeking Career Guidance After a 4-Year Gap

    hi I am new to this forum , i m really frustated regarding my career i have done masters in physics in India then started doing phd for 6 mnths (which i was not interested in) got married , came to usa, planned family . now I am 29 and want to start a career after 4 years of gap i got my...
  25. D

    Band Gap in Insulators: Values & Breakdown Voltage

    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...
  26. G

    How to calculate the gap for a solid?

    Hello everyone: Do you know how to calculate the energy gap (the forbitten band) for a solid from the Kroning-Penney model?
  27. J

    Band Gap in a Square Quantum Well

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

    Why is the mass gap of QCD so important?

    Ed Witten was essential in organizing the 1 million dollar prize for clarification of the mass gap in QCD that is offered by the Clay institute. But why is this issue so important? Wouldn't all the successes of QCD stay also if no glueballs existed? Can somebody explain why Witten wants the...
  29. Y

    N-carriers, number density, energy gap E_g, temperature

    hi folks, I've gotten most of this problem but for one part. I've learned quite a bit reading about the physics involved here on the web, but for all I've learned when I apply it, it doesn't work (ie give the right answer). So, I'm missing something. Homework Statement In silicon, E_g =...
  30. A

    Band Gap Formation: Bragg Reflection & Standing Waves

    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
  31. C

    Deriving equation for the magnetic field of a variable gap magnet

    I'm being asked to derive the equation for the magnetic field produced by a variable gap magnet. I've been given a few clues, but thus far have been unable to actually complete the derivation. The final equation should be: B_{ext}=\frac{mg}{lR}\left(\frac{d}{i}\right) I'm told I need to...
  32. V

    Schools University, Reapplying and Gap Year Options

    I'm a student in the UK, and have already applied, been rejected/accepted by various universities, and accepted a firm and insurance offer. I was accepted at Southampton, after rejections from Oxford and Imperial. I was happy with my decision, but after talking to my head of physics, I'm...
  33. L

    Absorption of photons with less energy than the band gap

    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...
  34. A

    Find band gap, energy gap for semiconductor using software

    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...
  35. G

    Electrons with in the forbidden gap

    Hi all, on one side we say that probability of finding electron with in the forbidden gap is zero, on other side we define fermi level as highest filled energy level(at absolute zero) lying in the mid of forbidden gap.Also for(T>0) probability of finding electron is 1/2 upto fermi level. So...
  36. I

    Highery energy photon on lower band gap semiconductor

    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...
  37. A

    Semiconductor Band Gap: Fermi Momentum & Dispersion Relation

    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...
  38. B

    Cyclotron accelerating protons to 20 MeV with potential gap 100 kV

    Homework Statement A Cyclotron is accelerating proton, where the applied magnetic field is 2 T, the potential gap is 100 KV, then how much turn are required for a kinetic energy of 20 MeV... (a) 300 (b) 200 (c) 150 (d) 100
  39. madmike159

    Why do blue LEDs have a higher forward voltage than expected?

    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...
  40. N

    What Does It Mean When the Fermi Level is in the Band Gap?

    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...
  41. I

    What's so special about Cu, Ag, and Au? fermi level? band gap?

    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 /...
  42. A

    Exploring the Employment Gap & MRP: Suggesting Reasons & Solutions

    I've come across a question which talks about the employment gap and asks me to suggest reasons on how it would occur. I thought better qualification could improve skills. I got this correct but I have to expand. Can someone explain how I can talk about MRP? Thanks in advance. :smile:
  43. S

    Bang Gap of Semiconductors: Exploring the Brus Approximation

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

    Relation between gap and order in spin model

    what is the definition of spin gap?I may have ever heard a conclusion that spin gap will not exist while the system present long range order(right?),but the system of XXZ model in external field could stay in ferromagnetic phase,and have a long range order with a gapped excitation.why?
  45. G

    How Does Temperature Affect GaP Life and Cause Peak Displacement in GaNP?

    GaP life question!?? Hi, i have a question. I hope someone could help me... Thenks in advance! 1.- I've read that the GaP life is sensitive to the temperature. Can you explain this in more detail?! I mean, what happens at low and high temperature and why. 2.- I've been calculating DOS...
  46. V

    Calculating Photon Energy Needed to Exceed Fused Silica Glass Band Gap

    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...
  47. P

    What Is the Relationship Between Band Gap and Temperature in Germanium?

    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...
  48. F

    News Gap in life expectancy in U.S. growing

    I especially like this part: & lastly, universal health care would probably reverse the trend: http://www.iht.com/articles/2008/03/23/america/health.php
  49. E

    Understanding the Origin of Energy Gap in Kittel's Book

    [SOLVED] kittel page 166 Homework Statement In Figure 3 of Chapter 7 of Kittel's Solid-state physics book, it says that this is the key to understanding the origin of the energy gap. However I do not understand why. It seems like if you take the expectation value of either |\psi(-)|^2 or...
  50. G

    GaP Band Structure: Find Paper & Reference

    Hi again, first of all i want to thanks the replies to my previous posts. Second... I'm looking for a paper about the GaP band structure. Actually i only need the band structure tu compare it with mine but i need the reference to that paper, can you help me?? sorry for my bad english by the way...
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