Atmospheric pressure MOCVD growth of high-quality ZnO films on GaN/Al2O3 templates

In this paper, we present the epitaxial growth of high-quality ZnO thin films on GaN/c-Al2O3 templates by atmospheric pressure metal organic chemical vapor deposition (MOCVD) using deionized water (H2O) and diethyl zinc (DEZn) as the O and Zn sources, respectively. Surface morphology of the films studied by metal-phase interference microscopy and AFM showed that the growth of the ZnO films followed the regular hexagonal columnar structure with about 19 μm grain diameter. High-resolution X-ray double-crystal diffraction was used to investigate the structural properties of the as-grown films. The FWHMs of the (0 0 0 2) and ( 101¯2) ω-rocking curves were 182 and 358 arcsec, respectively, indicating the small mosaicity and low dislocation density of the films. The optical properties of the films were investigated by room temperature photoluminescence and temperature-dependent PL spectra. Free excitons XA and the n=2 state of FXA can be clearly observed at 3.375  and 3.419 eV at 10 K, respectively. The domination of the free exciton and the appearance of its four replicas strongly indicate the high quality of the film.