Relation between GaAs surface morphology and incorporation of hexagonal GaN into cubic GaN

Cubic GaN (c-GaN) layers were grown on GaAs(0 0 1) substrates by metalorgan ic vapor-phase epitaxy, using dimethylhydrazine as a nitrogen source. For t he investigated growth temperature region of 600-820 degrees C, only h-GaN whose c-axis is oriented in the [1 1 1]A or [(1) over bar (1) over bar 1]A direction was incorporated into c-GaN. This orientation anisotropy of h-GaN caused the anisotropy of the width of c-GaN(0 0 2) X-ray diffraction (XRD) peaks. By flattening the GaAs surface to the atomic level, the hexagonal c omposition was effectively reduced and the anisotropy in the width of XRD w as eliminated. The observed result was interpreted in terms of molecular st eps appearing on the GaAs surface. (C) 1999 Elsevier Science B.V. All right s reserved.