Phase Separation and Facet Formation During the Growth of (GaAs)(sub 1-x)(Ge(sub 2))(sub x) Alloy Layers by Metal Organic Vapour Phase Epitaxy

摘要

Metal organic vapour phase epitaxy (GaAs)1-x(Ge2)x alloy layers, 0 lesser than x lesser than 0.22, were grown at temperatures between 640 degrees and 690 degrees C, on vicinal (001) GaAs substrates. Phase separation occurred in all the layers. The phase-separated microstructure changed with alloy composition, growth temperature, and substrate orientation. In x approx. 0.1 layers grown at 640 degrees C, Ge segregation occurred on (115)B planes associated with a (115)B surface faceting. Increase in growth temperature led to the formation of large, (001)-oriented, irregular-shaped platelets of Ge-rich material. Growth on (115)B substrates resulted in a 'natural superlattice' of GaAs/Ge along the growth direction.