Defect and stress relaxation in HVPE-GaN films using high temperature reactively sputtered AlN buffer

The influence of high temperature buffer layers on the structural character istics of GaN grown by hydride vapour phase epitaxy on sapphire was investi gated. Strain relaxation as well as mismatch-induced defect reduction in th ick GaN layers grown on AlN buffer was microscopically identified using cat hodoluminescence and micro-Raman spectroscopy in cross-section of the films . The results were correlated with photoluminescence and Hall-effect data o f layers with different thicknesses. These relaxation processes were sugges ted to account for the specific defect distribution in the buffers revealed by high-resolution X-ray diffraction and transmission electron microscopy. (C) 2001 Elsevier Science B.V. All rights reserved.