Structure and properties of GaN films grown on single crystalline ZnO substrates by molecular beam epitaxy

Abstract

GaN films were grown on ZnO single crystal substrates with various orientations by a molecular beam epitaxy method. Particularly, applicability of ZnO substrates for growth of GaN along non-polar axis was examined by using ZnO substrates with (1 1 2¯ 0) or (1 0 1¯ 0) orientation and effect of lattice matched (In,Ga)N buffer layer on crystallinity of GaN films was also investigated. Epitaxial GaN films were obtained regardless of the absence of (In,Ga)N buffer layer, when ZnO substrates with c-face were used. In contrast, GaN films deposited on (1 1 2¯ 0) or (1 0 1¯ 0) face of ZnO exhibited complicated manner of lattice orientation. Epitaxial growth of GaN films along non-polar axis was achieved only when the GaN films were grown on (In,Ga)N buffer layer deposited on ZnO substrates of (1 1 2¯ 0) orientation.