Carbon Reduction Coevaporation Preparation In < Sub > 2 < / Sub > Ge < Sub > 2 < / Sub > O < Sub > 7 < / Sub > Film And Uv Photosensitive Properties Research

Ternary oxide semiconductor In2Ge207is an excellent candidate in solar-blind detection for its wide band gap of4.43eV which has an absorption wavelength of280nm. The objective of this dissertation is to prepare In2Ge207thin film by carbothermal co-evaporation, and to investigate its possibility as base material of metal-semiconductor-metal (MSM) ultraviolet photodetector.First, In2Ge207thin film was deposited by carbothermal reduction co-evaporation method using In2O3, GeO2powder as raw materials. Then, we investigated the influence of the annealing temperature and time on the film quality. It was found that the thin film crystallized In2Ge207when the annealing temperature at500℃. However, the GeO2structure was formed in the thin film whose surface was rough and uneven when the temperature at700℃. Besides, with increasing annealing time, the In2O3structure in the film began to disappear, the X-ray diffraction (XRD) inte and full width half maximum (FWHM) became narrower. According to optimization of the annealing parameters, we concluded that the optimal annealing temperature of In2Ge2O7prepared by carbothermal co-evaporation was about600℃.XRD results of the sample which annealed for5hours at optimal annealing temperature proved that all the diffraction peaks of could be indexed to a pure monoclinic In2Ge2O7crystal phase (Joint Committee on Powder Diffraction Standards (JCPDS):26-0768, a=6.658A, b=8.784A, c=4.926A). This result showed that the thin film was polycrystalline thin film with a single phase. A smooth and compact surface of the film was observed by scanning electron microscope (SEM), which was very suitable for the production of ultraviolet (UV) detector. High wavelength selectivity of the In2Ge2O7thin film in deep-ultraviolet (DUV) region was proved by reflection spectrum. X-ray photoelectron spectroscopy (XPS) results showed that the atomic ratio of In, Ge and O element was1:1.31:3.6, which was close to In2Ge2O7of1:1:3.5proportion.At last, we prepared the MSM ultraviolet photodetector based on the In2Ge2O7film, and Ⅰ-Ⅴ characteristic and time response were tested. The size of the MSM interdigital electrode was2000μm×1000μm with20pairs electrodes, and its electrode width, spacing, length were20μm,30μm,800μm respectively. The photosensitive area of the device was1.36mm2. At5V bias, the dark current and photocurrent were12μA,727μA respectively. The photocurrent was almost60times of dark current, which illustrated that the device has obvious UV response. The device showed a slow time response with a rise time of67s and a decay time of15s. The long response time could be contributed to the defects and dislocations in the thin film.