title: Microstructural and compositional characteristics of GaN films grown on a ZnO-buffered Si (111) wafer.
abstract: Polycrystalline GaN thin films have been deposited epitaxially on a ZnO-buffered (111)-oriented Si substrate by molecular beam epitaxy. The microstructural and compositional characteristics of the films were studied by analytical transmission electron microscopy (TEM). A SiO(2) amorphous layer about 3.5 nm in thickness between the Si/ZnO interface has been identified by means of spatially resolved electron energy loss spectroscopy. Cross-sectional and plan-view TEM investigations reveal (GaN/ZnO/SiO(2)/Si) layers exhibiting definite a crystallographic relationship: [111](Si)//[111](ZnO)//[0001](GaN) along the epitaxy direction. GaN films are polycrystalline with nanoscale grains ( approximately 100 nm in size) grown along [0001] direction with about 20 degrees between the (1l00) planes of adjacent grains. A three-dimensional growth mode for the buffer layer and the film is proposed to explain the formation of the as-grown polycrystalline GaN films and the functionality of the buffer layer.
authors.affiliation: Electron Microscopy Laboratory and State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China.
authors.forename: X H
authors.initials: XH
authors.lastname: Luo
authors.forename: R M
authors.initials: RM
authors.lastname: Wang
authors.forename: X P
authors.initials: XP
authors.lastname: Zhang
authors.forename: H Z
authors.initials: HZ
authors.lastname: Zhang
authors.forename: D P
authors.initials: DP
authors.lastname: Yu
authors.forename: M C
authors.initials: MC
authors.lastname: Luo