Phase Separation and Facet Formation during the Growth of (GaAs)1-x(Ge2)x Alloy Layers by Metal Organic Vapour Phase Epitaxy

Metal organic vapour phase epitaxy (GaAs)1-x (Ge2 )x alloy layers, 0<x<0.22,; were grown at temperatures between 640? and 690?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 0.1 layers grown at 640?C, Ge segregation occurred on {115}B planesassociated 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.