EFFECTS OF SUBSTRATE TYPE ON THE CHARACTERISTICS OF GAN EPITAXIAL-FILMS GROWN BY MOLECULAR-BEAM EPITAXY

Films of GaN have been grown simultaneously on three different substra tes, sapphire, silicon carbide and GaN, by molecular beam epitaxy. The structural and optical properties of the films have been studied usin g x-ray diffraction techniques and low-temperature photoluminescence s pectroscopy respectively. There is a clear correlation between the str uctural and optical properties of the film and the nature of substrate . The lattice parameter of the film is shown to depend on the type of substrate. The incorporation of shallow donors is also strongly influe nced. The effect of lattice parameter, mismatch and differential therm al expansion on film properties is discussed.