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Topic: Indirect bandgap

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Direct bandgap

	Indirect bandgap - Wikipedia, the free encyclopedia
		In semiconductor physics, an indirect bandgap is a bandgap in which the minimum energy in the conduction band is shifted by a k-vector, which is determined by the material's crystal structure.
		Semiconductors with an indirect bandgap are inefficient at emitting light.
		Silicon is an indirect bandgap semiconductor, and hence is not generally useful for light-emitting diodes or laser diodes.
	en.wikipedia.org /wiki/Indirect_bandgap (215 words)

	Direct bandgap - Wikipedia, the free encyclopedia
		Indirect bandgap semiconductors such as crystalline silicon cannot do so efficiently.
		The prime example of a direct bandgap semiconductor is gallium arsenide - a material commonly used in laser diodes.
		See indirect bandgap for an explanation of the connection between bandgap offset and light emission.
	en.wikipedia.org /wiki/Direct_bandgap (106 words)

	Indirect bandgap (Site not responding. Last check: 2007-10-21)
		In semiconductor physics an indirect bandgap is a bandgap in which the energy in the conduction band is shifted by a k - vector which is determined by the material's crystal structure.
		Silicon is an indirect bandgap semiconductor and is not generally useful for light-emitting diodes or laser diodes.
		Indirect bandgap semiconductors can absorb light however only occurs for photons with significantly more than the bandgap.
	www.freeglossary.com /Indirect_bandgap (201 words)

	On the horizon: a virtually perfect solar cell (Site not responding. Last check: 2007-10-21)
		The low bandgap of indium nitride suggests that by simply varying proportions of indium and gallium, it may be possible to create rugged, inexpensive devices that can convert the full spectrum of sunlight to electric current.
		A semiconductor's bandgap is not a physical space; rather it is the difference between the energy of the electrons in its filled valence band and the energy electrons would need to occupy its empty conduction band.
		That's because silicon is an "indirect bandgap " semiconductor, in which creation of an electron-hole pair requires participation of the crystal lattice vibrations, wasting a lot of an incoming photon's energy.
	www.lbl.gov /Science-Articles/Archive/MSD-perfect-solar-cell.html (672 words)

	Optoelectronic devices
		Direct bandgap semiconductors, i.e semiconductors for which the minimum of the conduction band occurs at the same wavevector, k, as the maximum of the valence band, have a stronger absorption of light as characterized by a larger absorption coefficient.
		For an indirect bandgap semiconductor, the conduction band is not vertically aligned to the valence band as shown in Figure 4.6.1(b).
		Since the absorption process in an indirect bandgap semiconductor involves a phonon in addition to the electron and photon, the probability of having an interaction take place involving all three particles will be lower than a simple electron-photon interaction in a direct bandgap semiconductor.
	ece-www.colorado.edu /~bart/book/book/chapter4/ch4_6.htm (2349 words)

	Britney Spears Guide to Semiconductor Physics: Indirect-gap semiconductors. (Site not responding. Last check: 2007-10-21)
		For indirect bad gap semiconductors, the conduction band can be crudely approximated by the following equation near the conduction band minimum.
		For light emitting devices, indirect band gap semiconductors are not at all promising.
		Indirect semiconductors have a poor internal quantum efficiency.
	www.britneyspears.ac /physics/indirect/indirect.htm (214 words)

	bandgap (Site not responding. Last check: 2007-10-21)
		In infrared photodiodes, a small band gap semiconductor is used to allow detection of low-energy photons.
		The ability to tailor the bandgap of a device is possible in semiconductor alloys (such as GaAlAs, InGaAs, InAlAs, etc...), and is sometimes referred to as bandgap engineering.
		Bandgaps can be either direct or indirect bandgaps.
	www.yourencyclopedia.net /Bandgap.html (352 words)

	Clefs44 Glossary page 1 (Site not responding. Last check: 2007-10-21)
		Photons of energy higher than the bandgap generate charge carriers by transition of the electrons between the two allowed bands.
		Depending on the way the atoms are arranged and on the energies of the peripheral electrons, the photons are able to pass through the bandgap causing phonons to be emitted (network vibration quanta) – the band is then referred to as an
		bandgap (as in silicon) – or not –;
	www.cea.fr /gb/publications/Clefs44/an-clefs44/clefs44_gloss_1a.html (810 words)

	Talk:Indirect bandgap - Wikipedia, the free encyclopedia
		Is this entirely correct: "Indirect bandgap semiconductors can absorb light, however this only occurs for photons with significantly more energy than the bandgap."
		Couldn't an indirect semiconductor absorb a photon with the bandgap energy, if the momentum vector of the photon was just right?
		No, because the momentum of a photon is very small compared to the momentum offset between CB and VB.
	en.wikipedia.org /wiki/Talk:Indirect_bandgap (145 words)

	Indirect realism (Site not responding. Last check: 2007-10-21)
		Indirect Realism is the view in cognitive psychology that perception functions via internal representations of external reality.
		Indirect realism is problematical because of Ryle's regress and the apparent need for a homunculus.
		These problems have led some philosophers to abandon realism and suggest the existence of dualism and others to propose, or suggest through emergentism, that some form of new physics is operating in the brain such as quantum mind, space-time theories of consciousness etc.
	www.kiwipedia.com /indirect-realism.html (98 words)

	bit-tech.net Forums - View Single Post - Essay about Light Emitting Diodes
		Silicon has an 'indirect bandgap' which means that the diode does not generate light.
		The width of the energy bandgap determines the colour of the light emitted by the LED.
		Indirect bandgap semiconductors with 'recombination centres' had to be used instead, but this gave an efficiency of less than 1%.
	forums.bit-tech.net /showpost.php?p=537874&postcount=17 (420 words)

	Fabrication of quantum confinement semiconductor light-emitting devices - Patent 5607876
		The consequence is that indirect gap materials are a thousand to a million times less efficient at light emission (i.e., less light and more heat are emitted from the electron-hole recombination) than direct gap materials.
		It is believed that one method for converting an indirect gap semiconductor to a direct gap semiconductor is to localize the wavefunctions of the carriers in the indirect gap material.
		It is therefore preferable to be able to tune the device by controlling the characteristics of the device itself, and thus it is among the other purposes of the present invention to facilitate improved tunability or switching of the output wavelength of the light emitting device.
	www.freepatentsonline.com /5607876.html (7389 words)

	Journal of Electronic Materials: Wide and narrow bandgap semiconductors for power electronics: A new valuation
		An advantage for some wide bandgap materials that is often overlooked is that the thermal coefficient of expansion (CTE) is better matched to the ceramics in use for electronic-packaging technology.
		The potential advantages of these wide bandgap devices include higher achievable junction temperatures and thinner drift regions (because of the associated higher critical-electric field values) that can result in much lower on-resistance than is possible in Si.1-3 There are, however, several disadvantages associated with the use of devices fabricated from wide bandgap materials.
		An advantage to the use of some wide bandgap materials that is often overlooked, however, is that the coefficient of thermal expansion (CTE) is better suited to the ceramics used today in packaging technology.
	www.findarticles.com /p/articles/mi_qa3776/is_200306/ai_n9244169 (1162 words)

	[No title] (Site not responding. Last check: 2007-10-21)
		Indirect semiconductors have the lowest minimum of E(k) for the conduction-band electrons and the highest maximum of the valence-band holes located at significantly different values of k (or p).
		Consequence: In a direct bandgap semiconductor, direct recombination can take place across the bandgap, accompanied by the simple emission of a photon to carry away the excess energy of the electron; there is no momentum deficit to worry about.
		In an indirect bandgap semiconductor, momentum conservation cannot be satisfied by simple photon Recombination of EHP in indirect bandgap semiconductors typically involves more complex processes (See chapter 3).
	users.ece.gatech.edu /~rkenan/3351/q-1-rev.htm (838 words)

	Indirect Procurement (Site not responding. Last check: 2007-10-21)
		Indirect bandgap 1: In semiconductor physics, an '''indirect bandgap''' is a bandgap in which the minimum 3: Semiconductors with an indirect bandgap are inefficient at emitting light.
		Indirect effect 1: '''Indirect effect''' is a principle of European Union Law] 5: ==Indirect effect and individuals== 11: ==Indirect effect and states==
		Thus an example could be to 'jump indirect on the r1 register' would mean that the next inst 3:, this value could be stored in a register and an indirect jump made based on that register; efficiently imp
	www.elusiveeye.com /side7215-indirect-procurement.html (498 words)

	Indirect bandgap - Encyclopedia Glossary Meaning Explanation Indirect bandgap (Site not responding. Last check: 2007-10-21)
		Indirect bandgap - Encyclopedia Glossary Meaning Explanation Indirect bandgap.
		Here you will find more informations about Indirect bandgap.
		The orginal Indirect bandgap article can be editet
	www.encyclopedia-glossary.com /en/Indirect-bandgap.html (265 words)

	gallium nitride (Site not responding. Last check: 2007-10-21)
		Gallium Nitride (GaN) is a wide bandgap semiconductor material used in optoelectronic, high power and high frequency devices.
		Until 1993, the only blue light emitting devices commercially available were based on Silicon carbide, which had an indirect bandgap, and so were not capable of sufficient brightness to be of wide interest.
		The development of the first high brightness GaN LED by Shuji Nakamura, working for the Nichia company in Japan, completed the range of primary colors, and made possible applications such as daylight visible full color LED displays, white LEDs and blue laser devices.
	www.yourencyclopedia.net /gallium_nitride.html (188 words)

	Read about Indirect bandgap at WorldVillage Encyclopedia. Research Indirect bandgap and learn about Indirect bandgap ... (Site not responding. Last check: 2007-10-21)
		Research Indirect bandgap and learn about Indirect bandgap here!
		bandgap in which the minimum energy in the
		Silicon is an indirect bandgap semiconductor, and hence is not generally useful for
	encyclopedia.worldvillage.com /s/b/Indirect_bandgap (205 words)

	Optoelectronic device using indirect-bandgap semiconductor material US Patent 5920078 (Site not responding. Last check: 2007-10-21)
		Silicon-based semiconductor devices ordinarily lack desirable optical properties because silicon's small, indirect band gap causes electrons to emit radiation with negligible quantum efficiency.
		This invention solves that problem by taking advantage of the change in the nature of the electron band gap when electron flow is confined within a one-dimensional channel known as a quantum wire.
		The problem stems from silicon's indirect band gap, which requires the energy produced in the recombination process to be dissipated in ways other than radiation.
	patents.nimblewisdom.com /patent/5920078-Optoelectronic-device-using-indirect-bandgap-semiconductor-material (3300 words)

	Introduction to dilute nitrides (Site not responding. Last check: 2007-10-21)
		These materials are however limited to medium and narrow bandgap applications, preventing the fabrication of wide gap devices such as high power electronics and short wavelength optoelectronics.
		Despite the indirect bandgap of SiC, it was used in the late eighties to produce the first commercial blue LEDs; unfortunately, the indirect gap meant low efficiencies (~0.03 % [2]) and no scope for producing lasers.
		Increasing the In:Ga ratio causes a reduction in bandgap and an increase in lattice parameter, while increasing the N:As ratio also causes bandgap reduction, but a decrease in the lattice parameter.
	wave.prohosting.com /rjpott/DiluteNitrides.html (1227 words)

	Direct bandgap - TheBestLinks.com - Momentum, Physics, Silicon, Semiconductor, ... (Site not responding. Last check: 2007-10-21)
		Direct bandgap - TheBestLinks.com - Momentum, Physics, Silicon, Semiconductor,...
		Direct bandgap, Momentum, Physics, Silicon, Semiconductor, Conduction band...
		You can add this article to your own "watchlist" and receive e-mail notification about all changes in this page.
	www.thebestlinks.com /Direct_bandgap.html (142 words)

	Talk:Band gap - Wikpedia (Site not responding. Last check: 2007-10-21)
		Your two new articles (direct bandgap and indirect bandgap) were not introduced properly, and were too hard to understand for someone who didn't already know it.
		Perhaps just saying that the bandgap is related to the lattice spacing, and that changes with temperature...
		It might actually be good to show one of those classic figures where they show the difference between a metal, insulator, and semiconductor, insofar as the bandgap.
	www.bostoncoop.net /~tpryor/wiki/index.php?title=Talk:Band_gap (792 words)

	Novel Silicon Raman Laser Demonstrated on CMOS Chip - February, 2005 (Site not responding. Last check: 2007-10-21)
		But one stumbling block has stood firmly in the way of such integration: Silicon, the material of all semiconductor electronics, is an indirect- bandgap material.
		In a silicon Raman laser, photons are created not by the recombination of an electron and a hole, but by scattering of the pump light from a lattice vibration.
		Thus, silicon's indirect bandgap is not a consideration in a Raman laser.
	www.photonics.com /spectra/tech/XQ/ASP/techid.1683/placement.HomeIndex/QX/read.htm (1210 words)

	Question About Indirect vs. Direct Bandgap Semiconductors - Physics Help and Math Help - Physics Forums
		But to date most of the technologically exploited III-V semiconductor compound are direct bandgap (GaAs, InP etc), while group IV are indirect (eg Si, Ge).
		Lets say Si and Ge where both have the same structure, the only difference is the 18 extra electrones, but Si have an indirect bandgap and Ge a direct.
		In indirect semiconductors (Si) electron got some energy in minimum conduction band and mediator needed for transferring energy (phonons usually) in recombination process.
	www.physicsforums.com /showthread.php?goto=lastpost&t=45235 (823 words)

	Ge photodetectors patent (Site not responding. Last check: 2007-10-21)
		[0015] Ge is an indirect semiconductor whose bandgap is 0.667 eV corresponding to 1850 nm.
		Because of indirect bandgap characteristics, the absorption coefficient is small, approximately 100 cm.sup.-1 depending on the wavelength.
		The direct bandgap of Ge is 0.8 eV corresponding to 1550 nm.
	www.freshpatents.com /Ge-photodetectors-dt20050224ptan20050040411.php (1696 words)

	Diode laser with tunnel barrier layer - Patent 5509024
		As a result of the small valence-band discontinuity between the AlGaInP P-clad and the AlAs tunnel barrier (whether achieved by p-doping, or an inherently small offset), the increase in the effective electron barrier height is determined by the.GAMMA.-bandgap energy difference between the P-clad and tunnel barrier layers.
		The lower bandgap of Al.sub.x Ga.sub.1-x As, however, compromises barrier height, and so does not make an as effective tunnel barrier layer.
		Likewise, since the tunnel barrier layer is thin, it needn't be constructed of a lattice-matched material.
	www.freepatentsonline.com /5509024.html (2297 words)

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