White X‐ray microbeam analysis of strain and crystallographic tilt in GaN layers grown by maskless pendeoepitaxy

Abstract

AbstractWe describe X‐ray and finite element analysis of dislocations, strain and crystallographic tilt in uncoalesced GaN layers grown by maskless pendeoepitaxy. The experimental results reveal that the GaN wings are tilted upward at room temperature. The distribution of strain and tilt depends on the width‐to‐height ratio of the GaN column. As the width‐to‐height ratio increases the wing tilt increases and changes more abruptly at the column/wing interface. Broadening of the GaN Laue reflections is more pronounced in the column region then in the wing region; this is in line with the inhomogeneity of both the strain and the defect density. A split in the Laue reflections from GaN films at the column/wing interface indicates the development of a low‐angle tilt boundary for samples with a large width‐to‐height ratio of the column. Spacing between the dislocations in the tilt boundary at the column/wing interface for GaN grown with maskless pendeoepitaxy is an order of magnitude larger than the dislocation spacing observed for masked lateral epitaxial growth. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)