Indium gallium arsenide
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Indium gallium arsenide (InGaAs) is a semiconductor composed of indium, gallium and arsenic. It is used in high-power and high-frequency electronics because of its superior electron velocity with respect to the more common semiconductors silicon and gallium arsenide. InGaAs bandgap also makes it the detector material of choice in optical fiber communication at 1300 and 1550 nm. Gallium indium arsenide (GaInAs) is an alternative name for InGaAs.
The indium content determines the two-dimensional charge carrier density.
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[edit] Properties
The optical and mechanical properties of InGaAs can be varied by changing the ratio of In and Ga, InxGa1−xAs. The InGaAs device is normally grown on an indium phosphide (InP) substrate. In order to match the lattice constant of InP and avoid mechanical strain, In0.53Ga0.47As, this composition has a cut-off wavelength of 1.68 μm.
By increasing the ratio of In further compared to As it is possible to extend the cut-off wavelength up to about 2.6 µm. In that case special measures have to be taken to avoid mechanical strain from differences in lattice constants.
GaAs is lattice mismatched to Ge by 0.08%. With the addition of 1.5% In to the alloy, InGaAs, becomes perfectly latticed matched to Ge. The complete elimination of film stress reduces the defect densities of the epi InGaAs layer compared to straight GaAs.
[edit] Applications
HEMT devices using InGaAs channels are one of the fastest types of transistor [1].
InGaAs is also a popular material in infrared detectors. It is widely replacing germanium as a detector material mainly due to lower dark current (internally generated current). It is used as the detector material in some short-wave infrared cameras. InGaAs also has lower multiplication noise than germanium when used as the active multiplication layer of an avalanche photodiode.
InGaAs can be used as a laser medium. Devices have been constructed operating at wavelengths of 905 nm, 980 nm, 1060 nm, and 1300 nm. InGaAs quantum dots on GaAs have also been studied as lasers.
In(.015)Ga(.985)As can be used as an intermediate band-gap junction in multi-junction photovoltaic cells with a perfect lattice match to Ge. The perfect lattice match to Ge reduces defect density, improving cell efficiency.
[edit] Safety and toxicity aspects
The toxicology of InGaAs has not been fully investigated. The dust is an irritant to skin, eyes and lungs. The environment, health and safety aspects of indium gallium arsenide sources (such as trimethylgallium, trimethylindium and arsine) and industrial hygiene monitoring studies of standard MOVPE sources have been reported recently in a review [2].
[edit] See also
[edit] References
- ^ InP and InGaAs transistor breaks 600GHz
- ^ 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
[edit] External links
[edit] Academic links
- NSM data archive at the Ioffe Institute, St. Petersburg, Russia
