Improvement of quality and strain relaxation of GaN epilayer grown on SiC substrate by in situ SiNx interlayer

Abstract

Improved structural quality and tensile stress releasing were realized in GaN thin films grown on 6H–SiC by metal organic chemical vapor deposition using an in situ porous SiNx interlayer. The SiNx was formed in situ in the growth chamber by simultaneous flow of diluted silane and ammonia, leading to the formation of a randomly distributed mask layer and induced lateral overgrowth similar to conventional epitaxial lateral overgrowth of GaN. The full width at half maximum (FWHM) of X-ray diffraction peaks decreases dramatically by the SiNx interlayer, indicating an improved crystalline quality. Also, it was found that the biaxial tensile stress in the GaN film was significantly reduced by in situ SiNx interlayer from Raman spectra. Low temperature photoluminescence spectra exhibited a narrower FWHM by the SiNx interlayer.