High quality GaN film growth on AlN buffer layer, pretreated with alternating pulsative supply of TMG and NH₃

High quality GaN films of low etch pit density (10⁷ cm^-2) have been prepared by metal organic chemical vapour deposition (MOCVD) on 6H-SiC substrate with Aln buffer layer. The buffer layer was pretreated by alternating pulsative supply (APS) of trimethyl gallium (TMG) and NH₃ gases. Nitrogen atom is expected to incorporate into the gallium cluster formed by APS process. The sizes of GaN grains at the initial stage have increased by the treatment. The photoluminescence spectrum of the resulting GaN films at 13 K shows sharp near band-edge emission peak at 3.47 eV with 12 meV of FWHM value. The PL intensity of donor-acceptor transition peak at 3.26 eV was reduced with decrease of defect density.