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. S

    Air gap flux density in DC machine

    Why is it that the air gap flux density is flat topped at no load. What happens to it's shape when machine is loaded?
  2. D

    Direct and Indirect Optical Band Gap

    I've been looking on journals and textbook, as well as internet. Does anybody know if there is an equation to find out the value of direct optical band gap and indirect optical band gap? What is the difference of optical band gap, direct optical bandgap and indirect optical bandgap? also...
  3. P

    Newton's Rings and Gap Size - See Attachment

    Homework Statement A shallowly curved piece of glass is placed on a flat one. When viewed from above, concentric circles appear that are called Newton’s rings. In order to see bright rings, the gap can be: 1. 0 2. 1/4λ 3. 1/2λ 4. λ Homework Equations 1/2 λ occurs when n2>n1...
  4. O

    Gap between two displaced spheres

    This was out of a physics book, but since it's just geometry, I thought this would be the best forum to ask about it. I was reading through a derivation of the far electric field of a uniformly polarized sphere, and the author used a trick where he modeled the sphere as two displaced spheres...
  5. W

    Band gap calculation,how to choose the Kpoints?

    hello, is there anyone who can help me in the band gap calculation. my situation is that: I can calculate the band gap of sigle crystalline graphene, because i know the high symmetrical pionts of the first Brillouin zone of an hexagonal crystalline(M-G-K-M). But the problem is that...
  6. B

    Programs Will taking a gap year during my degree hurt much?

    Hi, I'm going into my junior year and I was thinking of taking a gap year to do something entirely different than Physics. Do grad schools look down on people who took a gap year during the progress of their degree? Will they require you to explain what happened during that year? Thanks! :smile:
  7. M

    Exploring Gap Exponents and Their Significance

    Gap exponents are denoted like critical exponents for higher derivatives of Gibbs potential. \Delta_l' (\frac{\partial G}{\partial H})_T=G^{(1)}\propto (1-\frac{T}{T_c})^{-\Delta_1'}G^{0} (\frac{\partial^l G}{\partial H^l})_T=G^{(1)}\propto (1-\frac{T}{T_c})^{-\Delta_l'}G^{l-1} \alpha'...
  8. E

    Consequences of Yang-Mills and Mass Gap?

    What are the consequences of a possible solution to Yang-Mills existence and mass gap problem? Are the consequences only physical or they will also have applications to other branches of science or life? If yes, what are they?
  9. M

    Interpretation of 1D Band Gap in Metallic Systems

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  10. S

    Is Taking a Gap Year During Undergrad Beneficial For Graduate School Admissions?

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  11. M

    Newbie Questions on Band Gap and Fermi Level

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  12. J

    Difficult Schedule to Bridge Gap

    Hello everyone, I am one of those non-majors trying to get into graduate school (eventually). Long story short, I have a year left as a business major, during which time I will be taking Calculus 2 and the introductory physics w/lab sequence. I have recently met with both the graduate...
  13. P

    Spark plug/Igniter/Spark gap in PSpice

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  14. I

    Magnetic pull force with a gap

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  15. F

    Plan Sprinkler System Layout: Minimize # Circles for Max Coverage

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  16. C

    Solar efficiencies of photovoltaics in relation to the band gap energies?

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  17. M

    Pairing gap equation weak coupling

    In the limit of weak coupling, G\overline{ρ}<<1, the BCS pairing gap equation gives that Δ \propto exp(-1/G\overline{ρ}). \overline{ρ} is the level density.This cannot be developed as a power series in the interaction strength G. Does this imply that there is a phase transition between a...
  18. E

    Energy Gap of Intrinsic Semiconductors: Temperature Dependence

    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,...)
  19. D

    How Can I Improve My Spark Gap Switch for High-Speed Photography?

    Hi everyone , this is my first post here :) . I am an auto electrician , my hobby is photography. I am interested in high speed photography and have invented a new form of photography in a way . I call it 'superspeed photography' . It involves taking a picture of something that is triggered by...
  20. A

    Is an Age Gap a Deal Breaker in Dating?

    I'm going to go ahead and put this to the board, figure I might as well. I'm 30 years old, and a pretty quiet person. Friendly, polite, but stand-offish with most people. Anyway, enough with the background. There's a girl at my work who I think is great. She's gorgeous, a little reserved, and...
  21. N

    Is It Reasonable to Assume a Prime Gap of at Least 10 Before Twin Primes?

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  22. S

    Why Can't Electrons Occupy the Band Gap in a Material?

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

    Gap between the plates of a Thermal Electric Modules

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  24. E

    Exploring Element Band Gap: What Determines the Size and How Can It Be Altered?

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  25. Pythagorean

    Gap junction modulators for C. elegans

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  26. B

    Show that for a ferromagnetic material the field in the gap is given by?

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  27. S

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  28. M

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  29. S

    Calculating Energy Stored in a Capacitor with Varying Gap

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  30. N

    Energy gap calculation for semi-conductors.

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  31. Chronos

    What Causes Early Convective Instabilities in Supernova Explosions?

    Perhaps this explains the mass gap between neutron stars and stellar mass black holes. http://arxiv.org/abs/1110.1635 Missing Black Holes Unveil The Supernova Explosion Mechanism
  32. P

    Spark Gap & Current: Exploring the Impact on Circuits

    Does a spark gap increase the current in a circuit? My thinking is that the surrounding air is ionized and any "stripped" free electrons would add to the current.
  33. A

    Bridge Degree Between Electronics & Planetary Science?

    Does anyone here know of a possible bridge degree between a bachelor's deg in electronics engineering and a degree in planetary science? I plan to pursue degrees in astronomy and then planetary science without wasting my five years with electronics. Is it possible to link them? If so, what...
  34. S

    How to find the amount of inter record gap in a magnatic tape?

    hello i have a question given to me on a tutorial which is to find what is the largest IRG that will allow 80 percent of the tape to be data in 2400 foot magnetic tape has recording density 6400 Bpi and data records are 100 bytes and memory buffer is 10,000. i have been looking every where but i...
  35. Ivan Seeking

    News The wealth gap - 92% of Americans surveyed prefer Sweden over the US

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  36. B

    Cyclotron: Speed of Particle After 2nd Gap Crossing

    Homework Statement A cyclotron is a particle accelerator made of two electrodes shaped as two empty half-circles separated by a small gap. We consider the dees as lying on the x-y plane, having radius R, both with centre in the origin, and each occupying the semiplane of positive and...
  37. M

    Pseudogap and phonon gap. Does phonon (pseudo)gap exist?

    We all know that there exist pseudogap in superconductors and in metals (semimetals). Were there the experiments, aimed to find gaps analogues to pseudogap in phonon spectrum? Is pseudogap T* is connected with some change in phonon spectrum in some direction? The same question for...
  38. B

    Semiconductor quatum well find band gap question

    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...
  39. S

    3.5 FDD head size: size of the gap of the read/write heads

    3.5" FDD head size: size of the gap of the read/write heads I doubt anyone here knows the answer, but I thought I would ask anyway. I mean, I know not of a better forum on which to ask... Anyway, does anyone happen to know the size of the gap of the read/write heads of a 3.5" floppy disk...
  40. N

    The band gap discontinuity in DFT?

    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...
  41. L

    Understanding Bandgap Voltage Reference Circuits

    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...
  42. L

    Energy gap from conductivity- temperature graph

    Homework Statement Hi, I have some values of conductivity in some temperatures. 0.01 at 400 Kelvin 10 at 600 K 70 at 700 K 1000 at 1000 K And I'm asked to find the energy gap of this intrinsic semi- conductor. Homework Equations The Attempt at a...
  43. D

    TiO2 Band Gap Energy: Direct vs. Indirect

    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.
  44. Q

    Energy band gap of semiconductors

    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...
  45. T

    The Real Science Gap: An Overview

    http://www.miller-mccune.com/science/the-real-science-gap-16191/ Nothing Earth shattering to people in this group, but a nice summary of the problem.
  46. R

    Coulomb's gap and Wave Equation

    Hi all I was wondering if I could solve the schrodinger's equation to see the limiting velocity for a proton to tunnel through the coulomb gap in order for the first equation in the fusion reaction to occur Thanks a lot
  47. K

    Piecewise-linear ball complexes: calculations with GAP

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  48. I

    Exploring Entropy Gap Expansion: Quantum or Universal?

    I'm asking this in the classical physics forums, because I view it as basically a thermodynamics question, but I'm wondering if I should put it in either the relativity or astrophysics forum, or even the quantum forum, because this topic is generally talked about in terms of cosmology...
  49. D

    Heat Transfer and Determining the Proper Gap

    I am struggling a bit with this problem: I have a pipe with a constant surface temperature of 1100F. I also have a tank which cannot reach a temperature higher than 258F. I am trying to figure out the minimum distance between the two (in 80F air, which will be moving at a minimum of 5 ft/sec)...
  50. P

    Physics Physics undergrad/grad gap year: ideas?

    One of our college's physics seniors scored poorly on the physics subject GRE and is looking for something to do for a year while s/he studies for, and retakes this test. Our student would like to find an appropriate position at a lab (academic, industrial, government...) which provides enough...
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