Molecular beam epitaxial growth of high quality BeMgZnO single crystal films for ultraviolet photodetectors

High quality ZnO single crystal films and alloy films were prepared on sapphire substrate by molecular beam epitaxy. By studying the influence of growth parameters on quality, components and defect density of the film, repetitive and controllable epitaxial growth conditions were obtained, and the possible positions and effects of doping elements, Be and Mg, in the crystal were further studied. The high quality of film was verified by RHEED and TEM. It is found that with small ionic radius Be doped in the lattice is easy to produce lattice distortion, and has a certain probability of entering the interstitial position. However, Mg atoms have high solid solution in ZnO. Photoconductive, schottky junction and heterojunction UV photodetectors were further prepared and their physical properties were systematically studied. We found that the response speed of the device is greatly slowed down due to the space charge layer caused by O₂ adsorption，and the response time is optimized to a scale of microsecond by Be doping. Heterojunction devices have the advantages of self-drive and ultra-fast response, which can be used as self-powered devices in some unmanned and harsh working environments. This research gives guidence for application of ZnO in semiconductor optoelectronic devices.