Monocrystalline films were grown, with and without Si3N4 masks, onto GaN/AlN/6H-SiC(00•1) and GaN(00•1)/AlN(00•1)/3C-SiC(111)/Si(111) substrates by using metal-organic vapour-phase deposition. Scanning and transmission electron microscopy were used to study external microstructures and dislocation distributions, respectively. The dislocation densities in the films were reduced by at least 5 orders of magnitude, relative to the initial GaN seed layers. Tilts of 0.2º were observed, via X-ray diffraction, in portions of GaN epilayers which were grown over Si3N4 masks. Neither tilting nor low-angle boundaries were observed within areas of coalescence in material that was grown onto substrates without masks. A strong low-temperature photoluminescence band-edge peak, at 3.45eV, was comparable to one which was observed in GaN films that were grown onto 6H-SiC(00•1).

Pendeo-Epitaxial Growth of Thin Films of Gallium Nitride and Related Materials and their Characterization. R.F.Davis, T.Gehrke, K.J.Linthicum, T.S.Zheleva, E.A.Preble, P.Rajagopal, C.A.Zorman, M.Mehregany: Journal of Crystal Growth, 2001, 225[2-4], 134-40