Comparisons of structural and optical properties of ZnO films grown on (0001) sapphire and GaN/(0001) sapphire template by atmospheric-pressure MOCVD

摘要

In this paper, we compare the properties of ZnO thin films on (0001) sapphire and GaN/c-Al_2O_3 templates by atmospheric pressure metal-organic chemical vapor deposition (AP-MOCVD) using deionized water (H_2O) and diethylzinc (DEZn) as the O and Zn precursors, respectively. The atomic force microscopy (AFM) images exhibited that ZnO films grown on GaN/c-Al_2O_3 template had a regular hexagonal columnar and smooth morphology, and the ZnO grown on c-Al_2O_3 film had the hexagonal pyramid morphology. The full widths at half maximum (FWHMs) of the (0002) and (10-12) ω-rocking curves of ZnO film grown on GaN/c-Al_2O_3 template were 182 and 358 arcs, respectively, indicating the smaller mosaicity and lower dislocation density of the film compared to ZnO film grown on c-Al_2O_3. The room temperature PL spectra showed that the PL intensity ratio of the band-edge emission (BEE) to the deep-level emission (DLE) for the ZnO film on GaN/c-Al_2O_3 template was larger than that of the film on c-Al_2O_3 . Besides, the FX_C (or the first excited state of A exciton) and four phonon replicas could be clearly observed in ZnO film on GaN/c-Al_2O_3 template at 10 K compared to ZnO film on c-Al_2O_3.