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 diffractometry and synchrotron X-ray topography. Calculations of thermal stresses gave approximately same results as experimental stress indicating that most of the stress in the film is due to the difference in thermal expansion coefficient between the film and substrate. The lowest dislocation density (i.e. 6.64×108 cm−2) in GaN was estimated for the sample, which has the highest thickness of GaN layer. Also comparing two different 6H-SiC substrates grown by sublimation and Lely techniques, the substrate grown by sublimation was found to be the better substrate to grow GaN thin film with lower dislocation density. Synchrotron X-ray topography revealed a number of defects including mosaic structure or local bending, low angle grain boundaries, cracks and micropores. Micropores originated at the 6H-SiC substrate went all the way through GaN films as revealed in the reflection topographs.