Microstructural study of MBE-grown ZnO film on GaN/sapphire (0001) substrate

Single crystalline ZnO film is grown on GaN/sapphire (0001) substrate by molecular beam epitaxy. Ga 2 O 3 is introduced into the ZnO/GaN heterostructure intentionally by oxygen-plasma pre-exposure on the GaN surface prior to ZnO growth. The crystalline orientation and interfacial microstructure are characterized by X-ray diffraction and transmission electron microscopy. X-ray diffraction analysis shows strong c-axis preferred orientation of the ZnO film. Cross-sectional transmission electron microscope images reveal that an additional phase is formed at the interface of ZnO/GaN. Through a comparison of diffraction patterns, we confirm that the interface layer is monoclinic Ga 2 O 3 and the main epitaxial relationship should be and .