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Aluminium gallium arsenide (also gallium aluminium arsenide) ( Al_x Ga_1−x As) is a

semiconductor material A semiconductor is a material with electrical conductivity between that of a Electrical conductor, conductor and an Insulator (electricity), insulator. Its conductivity can be modified by adding impurities ("doping (semiconductor), doping") to ...

with very nearly the same lattice constant as GaAs, but a larger

bandgap In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the ...

. The ''x'' in the formula above is a number between 0 and 1 - this indicates an arbitrary

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

between GaAs and AlAs. The chemical formula ''AlGaAs'' should be considered an abbreviated form of the above, rather than any particular ratio. The bandgap varies between 1.42 eV (GaAs) and 2.16 eV (AlAs). For x < 0.4, the bandgap is direct. The

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

is related with the bandgap via the Kramers–Kronig relations and varies between 2.9 (x = 1) and 3.5 (x = 0). This allows the construction of Bragg mirrors used in VCSELs, RCLEDs, and substrate-transferred crystalline coatings. Aluminium gallium arsenide is used as a barrier material in GaAs based heterostructure devices. The AlGaAs layer confines the electrons to a gallium arsenide region. An example of such a device is a quantum well infrared photodetector ( QWIP). It is commonly used in GaAs-based red- and near- infra-red-emitting (700–1100 nm) double-hetero-structure laser diodes.

Safety and toxicity aspects

The toxicology of AlGaAs has not been fully investigated. The dust is an irritant to skin, eyes and lungs. The environment, health and safety aspects of aluminium gallium arsenide sources (such as trimethylgallium and arsine) and industrial hygiene monitoring studies of standard MOVPE sources have been reported recently in a review.

References

External links

* {{DEFAULTSORT:Aluminium Gallium Arsenide Arsenides Aluminium compounds Gallium compounds III-V semiconductors III-V compounds Light-emitting diode materials Zincblende crystal structure