High quality GaN layers grown by hydride vapor phase epitaxy - a high resolution X-ray diffractometry and synchrotron X-ray topography study

GaN films of different thicknesses grown on 6H-SiC (00.1) by hydride vapor- phase epitaxy(HVPE) method were characterized by high resolution X-ray diff ractometry and synchrotron X-ray topography, Calculations of thermal stress es gave approximately same results as experimental stress indicating that m ost of the stress in the film is due to the difference in thermal expansion coefficient between the him and substrate. The lowest dislocation density (i.e. 6.64 x 10(8) cm(-2)) in GaN was estimated for the sample, which has t he highest thickness of GaN layer. Also comparing two different 6H-SiC subs trates grown by sublimation and Lely techniques, the substrate grown by sub limation was found to be the better substrate to grow GaN thin film with ro wer dislocation density. Synchrotron X-ray topography revealed a number of defects including mosaic structure or local bending, low angle grain bounda ries; cracks and micropores. Micropores originated at the 6H-SiC substrate went all the way through GaN films as revealed in the reflection topographs . (C) 2000 Elsevier Science S.A. Al rights reserved.