Aluminium gallium arsenide (alsogallium aluminium arsenide) (AlxGa1−xAs) is asemiconductor material with very nearly the samelattice constant asGaAs, but a largerbandgap. Thex in the formula above is a number between 0 and 1 - this indicates an arbitraryalloy betweenGaAs andAlAs.
The chemical formulaAlGaAs should be considered an abbreviated form of the above, rather than any particular ratio.
The bandgap varies between 1.42eV (GaAs) and 2.16 eV (AlAs). For x < 0.4, thebandgap is direct.
Therefractive index is related with the bandgap via theKramers–Kronig relations and varies between 2.9 (x = 1) and 3.5 (x = 0). This allows the construction ofBragg mirrors used inVCSELs,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 inGaAs-basedred- and near-infra-red-emitting (700–1100 nm) double-hetero-structurelaser diodes.
The toxicology of AlGaAs has not been fully investigated. The dust is an irritant to skin, eyes and lungs. Theenvironment, health and safety aspects of aluminium gallium arsenide sources (such astrimethylgallium andarsine) and industrial hygiene monitoring studies of standardMOVPE sources have been reported recently in a review.[1]