The Properties Of The Sm₂O₃ Thin Film Heterojunction And Its Application In The Ultraviolet Photodetector

With the development of technology of the ultraviolet detection, ultraviolet photodetectors get more and more attention from people. The materials used in the preparation of UV photodetectors have experienced three stages of development: the first generation of semiconductor materials Si and Ge; the second generation of semiconductor materials GaAs,GaP and In As; and the third generation of semiconductor materials SiC, GaN, ZnSe, ZnO, etc.Although the third generation of semiconductor materials have many advantages, such as big band gap, small dielectric constant and big electron drift velocity, but as ultraviolet detection materials also, it is still not fully satisfactory, because of the lattice mismatch, bandwidth limitations and poor quality of thin film. So, it is necessary to find new materials for the ultraviolet detection.Rare earth oxides with high dielectric constant, large band gap width, good chemical stability,recently has been widely used in photoelectric device, electronic switch and memory device.Sm₂O₃ photoelectric material is one of the popular Ln oxides, and its electrical properties, optical properties has been widely studied. Especially because of its big dielectric constant, it is suited to replace SiO2 as the insulation of the transistor’s gate. But the reports applying Sm₂O₃ in UV detections are rare. The research purpose of this paper is to find a new material for UV detector,and study the material’s responsiveness to ultraviolet light.In this paper, through the sol-gel method and RF magnetron sputtering technology, we deposited Sm₂O₃ film on Si and quartz glass substrates. The crystal structure and surface morphology of the thin film were characterized. Then we prepared Sm₂O₃/n-Si heterostructure,and tested its photoelectrical properties. The main results achieved in this paper can be summarized as following:1. Sm₂O₃/n-Si heterojunctions were fabricated by depositing Sm₂O₃ film on n-Si substrate using spin coating method. The crystal structure, surface morphology and optical properties of the Sm₂O₃ thin film were characterized. The current-voltage characteristics（V-I） and photoresponse properties of the heterojunction were measured. It is found that there is a rectification of the Sm₂O₃/n-Si heterojunction and the heterojunction shows a fast and stable response to ultraviolet light and visible light, and the responsiveness changes with the numberof spin.The physical mechanisms of the measured properties in Sm₂O₃/n-Si heterojunction were explained using band structure diagram.2. Though radio frequency magnetron sputtering technique, Sm₂O₃/n-Si heterostructure were prepared by depositing Sm₂O₃ film on n-Si substrate. We explored the impact on the membrane structure and surface morphology by different sputtering factors（sputtering pressure,substrate temperature, sputtering power）. The opto-electronic and temperature dependent electrical transport properties of the fabricated device were also characterized. It is found that there is a rectification of the Sm₂O₃/n-Si heterojunction, but the rectification changes with the thickness of Sm₂O₃ thin film. The current conduction mechanisms of the rectification under different thickness all belong to Fowler-Nordheim. In the temperature range 10³00 K, the rectification has the same direction, and the rectification ratio increases with the increase of temperature. The electrical measurements show fast and stable photovoltaic behavior to ultraviolet light. There are large rectification ratio and On/Off current ratio under irradiation by ultraviolet light.3. We packaged Sm₂O₃/n-Si heterojunction with a metal shell, and there is good photoresponse to UV light of the packaged device. Then we completed the design of peripheral circuit. After the preparation of circuit board, welding of components and debugging of circuit,the uv detector can make fast and stable response to UV light.