- Indium gallium nitride
Indium gallium nitride (InGaN, IndiumxGallium1-xNitrogen) is a
semiconductor material made of a mix ofgallium nitride (GaN) andindium nitride (InN). It is a ternary group III/group Vdirect bandgap semiconductor . Itsband gap can be tuned by varying the amount of indium in the alloy. The ratio of In/Ga is usually between 0.02/0.98 and 0.3/0.7.Indium gallium nitride is the light-emitting layer in modern blue and green
LED s and often grown on aGaN buffer on a transparent substrate as, e.g.sapphire orsilicon carbide . It has a highheat capacity and its sensitivity toionizing radiation is low (like other group IIInitride s), making it also a potentially suitable material forsolar cell arrays forsatellite s.It is theoretically predicted that in a composition regime between ~ 15% -85% Indium nitride
spinodal decomposition should occur leading to In-rich and Ga-rich InGaN regions or clusters. However, local structure studies of InGaN did not show any evidence for strong phase segregation, despite signs of a weak phase segregation being observed [V. Kachkanov, K.P. O’Donnell, S. Pereira, R.W. Martin, Phil. Mag. 87(13), 1999–2017 (2007)] .GaN is a defect rich material with typical dislocation densities exceeding 108 cm-2.
Light emission from InGaN layers grown on such GaN buffers used in blue and green LEDs is expected to be low because of non-radiative recombination at such defects. Nevertheless InGaNquantum well s, are efficient light emitters in green, blue, white andultraviolet light-emitting diode s anddiode laser s. In the indium-rich regions, with a lower bandgap than the surrounding material, most electron-hole pairs recombine and by the lower potential energy of these clusters carriers are hindered to diffuse and recombine non-radiatively at crystal defects.The wavelength emitted, dependent on the material's band gap, can be controlled by the GaN/InN ratio, from near ultraviolet for 0.02In/0.98Ga through 390 nm for 0.1In/0.9Ga, violet-blue 420 nm for 0.2In/0.8Ga, to blue 440 nm for 0.3In/0.7Ga, to red for higher ratios and also by the thickness of the InGaN layers which are typically in the range of 2-3 nm.
This defect tolerance, together with a good spectral match to sunlight, also makes the material suitable for
solar cell s. It is possible to grow multiple layers with different bandgaps, as the material is relatively insensitive to defects introduced by a lattice mismatch between the layers. A two-layer multijunction cell with bandgaps of 1.1 eV and 1.7 eV can attain a theoretical 50% maximum efficiency, and by depositing multiple layers tuned to a wide range of bandgaps an efficiency up to 70% is theoretically expected. [ [http://www.lbl.gov/Science-Articles/Archive/MSD-perfect-solar-cell-2.html A nearly perfect solar cell, part 2 ] ]Quantum heterostructure s are often built from GaN with InGaN active layers.InGaN is often used together with other materials, eg. GaN, AlGaN, on SiC,
sapphire and evensilicon etc.afety and toxicity aspects
The toxicology of InGaN has not been fully investigated. The dust is an irritant to skin, eyes and lungs. The environment, health and safety aspects of indium gallium nitride sources (such as
trimethylindium ,trimethylgallium andammonia ) and industrial hygiene monitoring studies of standardMOVPE sources have been reported recently in a review [Environment, health and safety issues for sources used in MOVPE growth of compound semiconductors; D V Shenai-Khatkhate, R Goyette, R L DiCarlo and G Dripps, Journal of Crystal Growth, vol. 1-4, pp. 816-821 (2004); doi|doi:10.1016/j.jcrysgro.2004.09.007] .ee also
*
Indium gallium phosphide
*Indium gallium arsenide
*Shuji Nakamura References
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