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 (10(7) cm(-2)) have been pre pared by metal organic chemical vapour deposition (MOCVD) on 6H-SiC substra te with Aln buffer layer. The buffer layer was pretreated by alternating pu lsative supply (APS) of trimethyl gallium (TMG) and NH3 gases. Nitrogen ato m is expected to incorporate into the gallium duster formed by APS process. The sizes of GaN grains at the initial stage have increased by the treatme nt. 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. T he PL intensity of donor-acceptor transition peak at 3.26 eV was reduced wi th decrease of defect density. (C) 1999 Elsevier Science B.V. All rights re served.