Preparation Of ZnO-base Sandwich Structure UV Detector And Performance Of Gain

In recent years,UV detection technology has been widely used in chemical,environmental and biological analysis,flame and radiation detection,astronomical research,optical communication and missile early warning and other civil and military fields.With the rapid development of these fields,the demand for UV detection is increasing day by day.High performance UV detector as the core of UV detection technology has been widely concerned.In numerous ultraviolet detection material,ZnO materials as a typical wide bandgap semiconductor material,because of its high exciton binding energy,has the lattice matching substrate,abundant resources,no pollution to the environment and by doping Mg element can realize the wide band gap(3.37 ? 7.8 e V)the advantage such as the adjusting range and has been widely concerned.However,the current common metal-oxide-metal(MSM)ZnO based UV detectors are faced with the problems of low quantum efficiency and lack of controllable gain mode.In view of the shortcomings and key problems of ZnO based UV detectors,a sandwich ZnO based UV detector was prepared by magnetron sputtering technology on the basis of MSM structure.By increasing the Schottky contact area and constructing the MgZnO/ZnO junction,the gain and external quantum efficiency of the ZnO based UV detector were greatly improved,and the mechanism of its performance improvement was systematically analyzed.The main research results are as follows:(1)Based on the traditional MSM structure,the ZnO/Au/ZnO sandwich structure UV detector was prepared by RF magnetron sputtering technology.By realizing backlight irradiation,the area of the active layer of the device is greatly improved,and the photoelectric conversion efficiency of the device is improved.In addition,the Schottky junction formed by more Schottky contacts also accelerates the separation of photoelectron-hole pairs,which greatly increases the internal gain of the device.In general,the gain and external quantum efficiency of the detector are improved obviously.The responsiveness of ZnO/Au/ZnO sandwich UV detector at 25 V bias reaches 3.32 A/W,and the external quantum efficiency reaches 1100%.The results show that the performance of the sandwich structure detector is significantly better than that of the MSM structure ZnO UV photoelectric detector,and the responsiveness is 5.73 times that of the MSM structure ZnO UV photoelectric detector(0.58A/W).(2)To solve the problem of low external quantum efficiency and lack of controllable gain mode of MSM structure detector,the MgZnO/Au/ZnO sandwich structure UV detector was prepared by MgZnO/ZnO energy band engineering on the basis of ZnO/Au/ZnO sandwich structure,which further improved the gain and external quantum efficiency of the device.The MgZnO/Au/ZnO sandwich structure UV detector uses the band bending formed between MgZnO/ZnO to rapidly separate the photogenerated electron-hole pair,and improves the performance of the device by increasing the concentration of the effective photogenerated carrier.The outer quantum efficiency of the MgZnO/Au/ZnO sandwich UV detector at 314 and 364 nm reaches 533% and 1120%,respectively,at 40 V bias.Then,by increasing the Mg content in the MgZnO film,the increase factor of the responsiveness of MgZnO was increased to 12.56.(3)By optimizing the sputtering parameters,a single six-direction MgZnO film with a Mg content of 57.6% was deposited on the quartz substrate.Under 40 V bias,the response peak of MgZnO UV detector successfully entered the solar-blind band(275 nm),and the responsiveness reached 0.05 A/W.On this basis,an innovative avalanche effect was realized in MSM structure by preparing MgZnO/Au/ZnO sandwich structure,which greatly improved the internal gain and external quantum efficiency of the device.The avalanche voltage of the MgZnO/Au/ZnO sandwich avalanche detector is less than 65 V,and the avalanche factor reaches 98 at a bias voltage of 90 V.Thanks to the high gain of the avalanche effect,the responsiveness and external quantum efficiency of the MgZnO/Au/ZnO sandwich UV detector under 275 nm light reach 1115.18 A/W and 502780%,respectively.