Growth of GaN on on-axis 6H-SiC (00•1)Si substrates with an AlN buffer layer was performed by molecular-beam epitaxy. The effects of SiC surface reconstruction on the lattice relaxation of AlN buffer layers and the crystalline quality of GaN layers were studied. High-temperature HCl-gas etching followed by HF chemical treatment resulted in an atomically flat SiC surface with a 1 x 1 structure. The AlN layer grown on the surface showed slow lattice relaxation. GaN grown on the AlN buffer layer exhibited the narrowest (00•2) X-ray rocking curve of 70arcsec and 107/cm2 screw-type dislocation density, which was 2 orders of magnitude smaller than that of GaN grown on as-received substrates.

Effects of 6H-SiC Surface Reconstruction on Lattice Relaxation of AlN Buffer Layers in Molecular-Beam Epitaxial Growth of GaN. J.Suda, K.Miura, M.Honaga, Y.Nishi, N.Onojima, H.Matsunami: Applied Physics Letters, 2002, 81[27], 5141