Crack-free Al0.5Ga0.5N epilayer grown on SiC substrate by in situ SiNx interlayer

The crystal quality and stress state of Al0.5Ga0.5N epitaxial layers on 6H-SiC wafers by introducing an in-situ deposited SiNx nanomask layer grown by metal-organic chemical vapor deposition (MOCVD) were investigated. A SiNx interlayer with various growth times was inserted to the Al0.5Ga0.5N epilayers. The full width at half maximum (FWHM) of X-ray diffraction peaks and the density of etch pits decreased dramatically by the SiNx interlayer, indicating an improved crystalline quality. Also, it was found that the crack density and biaxial tensile stress in the Al0.5Ga0.5N film was significantly reduced by in situ SiNx interlayer from optical microscopy, photoluminescence spectra and Raman spectra. Finally, a crack-free 1.8 μm thick Al0.5Ga0.5N epilayer grown on 6H-SiC substrate using the optimized SiNx interlayer growth time was obtained.