Structural and optical properties of ZnO films grown on ion-plated Ga doped ZnO buffer layers by atmospheric-pressure chemical vapor deposition using Zn and H2O as source materials

Zinc oxide (ZnO) films were grown on glass substrates with ion-platedGa-doped ZnO (GZO) buffer layers at various substrate temperatures by atmospheric-pressure chemical vapor deposition using Zn powder and water as precursors. All the X-ray diffraction patterns of the ZnO/GZO films were dominated by a ZnO(002) peak, indicating the successful growth of highly c-axis oriented films. The substrate temperature dependence of growth rate was divided into three regions with the different activation energies, i.e. re-evaporation, mass-transport controlled and surface-controlled regions. Scanning-electron-microscope observations revealed that the films grown at the substrate temperature in the mass-transport-controlled region exhibited the terrace-like surface morphology with rock-like structures. Photoluminescence spectra of the ZnO/GZO films were composed of a near-band-edge (NBE) emission at a wavelength of about 380 nm and a broad-band emission spreading over the visible wavelength region, as regardless of the substrate temperature. The visible-broad-band emissions observed on many samples could be decomposed into two or three peak emissions with the Lorentzian shapes. With increasing substrate temperature, the wavelength of the emission showing the strongest intensity, which was obtained by the decomposition of the visible-broad-band emission, shifted towards longer wavelengths together with the broadening of its width.