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 metalorganic vapor-phase epitaxy, using dimethylhydrazine as a nitrogen source. For the 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 composition was effectively reduced and the anisotropy in the width of XRD was eliminated. The observed result was interpreted in terms of molecular steps appearing on the GaAs surface. (C) 1999 Elsevier Science B.V. All rights reserved.