Aluminium arsenide-gallium arsenide epitaxial layer structure

摘要

In an epitaxial layer structure used for luminescent devices based on AlAs/GaAs heterojunctions and produced by gas phase epitaxy, an intense short wave luminescence in the blue to red spectral range is produced in the layer structure which consists of a periodic stacking of respectively 2 monolayers or up to 7 monolayers of GaAs embedded in 7 nm AlAs. The MOVPE grown interfaces between the direct GaAs and indirect AlAs semiconductor layers cause conventional low energy luminescence from the X level of the AlAs conduction band to the F level of the GaAs valence band to be minimised so that the higher energy transitions in the 2 or up to 7 monolayers thick GaAs quantum wells can be used for intense short wave emission. Also claimed is a process for producing the above epitaxial structure, in which low pressure MOVPE is carried out at 50 mbars, using trimethyl aluminium, trimethyl gallium, trimethyl indium, arsine and phosphine in a hydrogen atmosphere, at a growth temperature of above 750 deg C and a growth rate of 1 monolayer per sec. to produce interfaces in the AlAs/GaAs superlattice such that low energy emission of type 2 transition is minimised preferentially wrt. the high energy type 1 transition.