{{Short description|Semiconductor material}} [[File:Sphalerite-unit-cell-depth-fade-3D-balls.png|thumb|The crystal structure of aluminium gallium arsenide is [[Zincblende (crystal structure)|zincblende]].]] '''Aluminium gallium arsenide''' (also '''gallium aluminium arsenide''') ([[Aluminium|Al]]<sub>x</sub>[[gallium|Ga]]<sub>1−x</sub>[[arsenic|As]]) is a [[semiconductor material]] with very nearly the same [[lattice constant]] as [[Gallium arsenide|GaAs]], but a larger [[bandgap]]. The ''x'' in the formula above is a number between 0 and 1 - this indicates an arbitrary [[alloy]] between [[Gallium arsenide|GaAs]] and [[Aluminium arsenide|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 [[electron volt|eV]] (GaAs) and 2.16 eV (AlAs). For x < 0.4, the [[direct bandgap|bandgap is direct]].

The [[refractive index]] 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 mirror]]s used in [[VCSEL]]s, [[RCLED]]s, 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&nbsp;nm) double-hetero-structure [[laser diode]]s.

==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.<ref>{{ cite journal |author1=Shenai-Khatkhate, D. V. |author2=Goyette, R. J. |author3=DiCarlo, R. L. Jr. |author4=Dripps, G. | journal = Journal of Crystal Growth | year = 2004 | volume = 272 | issue = 1–4 | pages = 816–821 | doi = 10.1016/j.jcrysgro.2004.09.007 | title = Environment, Health and Safety Issues for Sources Used in MOVPE Growth of Compound Semiconductors |bibcode=2004JCrGr.272..816S }}</ref>

==References== {{reflist}}

==External links== * {{ cite web | url = http://www.ioffe.ru/SVA/NSM/Semicond/AlGaAs/index.html | work = Ioffe Database | title = Al<sub>x</sub>Ga<sub>1−x</sub>As | publisher = FTI im. A. F. Ioffe, RAN | location = Sankt-Peterburg }}

{{Aluminium compounds}} {{Gallium compounds}} {{Arsenides}}

{{DEFAULTSORT:Aluminium Gallium Arsenide}} [[Category:Arsenides]] [[Category:Aluminium compounds]] [[Category:Gallium compounds]] [[Category:III-V semiconductors]] [[Category:III-V compounds]] [[Category:Light-emitting diode materials]] [[Category:Zincblende crystal structure]]