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Published online by Cambridge University Press: 28 February 2011
Defect structures in thin, MBE grown, GaAs/Si(001) heteroepitaxial films were studied with grazing incidence x-ray scattering techniques. The diffuse scattering associated with GaAs having the predominant epitaxial orientation varied strongly with the penetration depth of the x-rays. Well directed streaks corresponding to planar faults were observed and easily distinguished from a broad and more randomly oriented background. Bragg peaks corresponding to twinned GaAs were also studied. The probability of twinning was seen to be much higher about the {111} planes whose normals, when projected onto the sample surface, lay parallel to the off-orientation direction than about the {111} planes whose normals, when projected onto the sample surface, lay perpendicular to the off-orientation direction. The intensity and breadth of the twin reflections were analyzed to estimate the corresponding defect density. The depth dependence of the twinning probability was seen to vary with growth parameters.