CHARACTERIZATION OF MICROCRYSTALLINE GAN GROWN ON QUARTZ AND ON SAPPHIRE BY LASER AND MICROWAVE PLASMA-ENHANCED METALORGANIC CHEMICAL-VAPOR-DEPOSITION

We present a comparative study of GaN grown on quartz and on sapphire by laser assisted metalorganic chemical vapour deposition. Films were characterised by X-ray diffraction, Raman spectroscopy and optical tra nsmission. Films grown on both substrates are polycrystalline, with th e dominant orientation of (0002) wurtzite or (111) cubic for growth te mperatures 550 degrees C and lower. In films frown at 625 degrees C, b oth on quartz and on sapphire the crystallites show a variety of orien tations, all attributed exclusively to wurtzite phase. Films grown at the same temperature are characterised by similar value of the Urbach parameter for both substrates. The Raman spectra in all examined films are alike, and characteristic for a disordered cubic GaN.