Morphology Controllable ZnO Growth on Facet-Controlled Epitaxial Lateral Overgrown GaN/Sapphire Templates

High-quality epitaxial ZnO layers grown on facet-controlled epitaxial lateral overgrown (FACELO) GaN/sapphire templates were achieved by an evaporation-physical transport-condensation method. The ZnO/FACELO GaN heterostructures showed a substantial improvement in the crystalline quality with a lower defect density and excellent photoluminescence emission. The effects of the growth temperature and oxygen flow rate on the morphology of ZnO were systematically studied. The determining factors for the formation of different morphologies were found to be gas-phase supersaturation and the surface energy of the growing planes. In addition, the lattice matching between the ZnO and GaN leads to the improvement of the electric and optical properties. With such kind of perfect ZnO/GaN heterostructure interfaces obtained on the semipolar (11,(2)over bar>2) surface, the new opportunities for the fabrication of hybrid ZnO/GaN optoelectronic devices on sapphire are proposed.