INTERFACIAL DEFECTS AND MORPHOLOGY OF INGAAS EPITAXIAL LAYERS GROWN ON TILTED GAAS SUBSTRATES

Systematic transmission electron microscopy studies of In0.2Ga0.8As la yers grown by molecular-beam epitaxy on [001] GaAs substrates and on s ubstrates tilted up to 10-degrees toward [110], [120], [100], [110BAR] , and [120BAR] are described. Three different layer thicknesses were i nvestigated: 6, 20, and 40 nm. In the 40 nm layers misfit dislocations were formed which partially relaxed the elastic strain. Three-dimensi onal growth with an indication of microscale In segregation (dendritic growth) occurred for substrates tilted toward [110BAR] and [120BAR] d irections. Smooth growth surfaces were observed when the substrates we re tilted toward [110] and [120] showing that the chemistry of the pre dominant surface growth steps can play an important role in the growth mode and quality of the epitaxial layer. Indium segregation to misfit dislocation cores, the presence of In-rich platelets near the interfa ce, and diffuseness of the interface are considered as evidence for sh ort range migration of In during and after growth.