Study On TiO₂ UV Detector Based On Built-in Electric Field Effect

With the rapid development of science and technology in recent years,great breakthroughs have been made in the research of ultraviolet?UV?detection.UV detection technology is widely used in medicine,military,life and other aspects of life.First of all,in medicine,ultraviolet detection technology can help to detect the changes of human cells,so as to prevent the occurrence of diseases;secondly,in people's daily life,ultraviolet detection technology is mainly used to detect the ultraviolet produced by the flame combustion,so as to achieve the goal of fire prevention;in national security,ultraviolet detection technology is often used to detect missile tail flame.In addition,UV detector has been widely studied because of its simple fabrication,excellent performance,safety and practicality.In recent years,the wide band gap ultraviolet detector is developing with the advantages of easy fabrication and high photocurrent,among which the common materials are TiO₂,ZnO,NiO,etc.However,because the performance of the UV detector made of a single material has reached its bottleneck,people began to seek the combination of composite materials and wide band gap materials to prepare new ultraviolet detectors..The method of doping materials can further improve the photoelectric performance parameters of the UV detector.The introduction of doping materials can effectively improve the dark current and low response of the UV detector.The main research work of this paper is as follows:In the second chapter,the uv detector was made by doping C quantum dots?QDs?into TiO₂ nano films.the UV detector uses metal semiconductor metal structure.The TiO₂ thin film is prepared by sol-gel method.C QDs is synthesized by reaction vessel under high temperature and high pressure.Due to the large difference of work functions between TiO₂and C QDs,a local built-in electric field(E_bi)is formed around the C QDs when they are contacted.When the detector works under ultraviolet light,the local built-in electric field in composite film can promote the separation of hole electron pairs in TiO₂ material,which is conducive to the transmission and collection of photogenerated carriers;In the dark state,the local built-in electric field in the composite film can bind some carriers in the transmission,thus effectively reducing the dark current of the detector.The performance of the uv detector doped with C QDs has been greatly improved.Firstly,the dark current of TiO₂:C-2 device under 5 V bias is 1.58×10^-9A,which is twice as low as that of TiO₂device;under 300 nm illumination,the photocurrent is 4.32×10^-6A,which is 5 times higher than that of TiO₂ device;in addition,the photocurrent suppression ratio of TiO₂:C-2device is 2.03×10³ at 300 nm.In the second chapter of this paper,the fabrication method of TiO₂ doped C QDs.UV detector is introduced in detail,and the performance of the detector is tested and compared,and the working principle of TiO₂:C UV detector is analyzed in depth.In chapter 3,the P-type wide-gap BiClO nanometer block is introduced to prepare the uv detector.Under thermal equilibrium conditions,when N-type TiO₂ is in contact with P-type BiClO,the built-in electric field is formed through carrier diffusion to improve the performance of the detector.In the experiment,BiClO nano block was synthesized by hydrothermal method,and a series of TiO₂:BiClO detectors were prepared on the premise of good film-forming ability of dopant solution.By comparing the test results of TiO₂detector with that of TiO₂:BiClO detector with different concentrations,it can be concluded that the dark current of TiO₂:BiClO device is decreasing with the increase of doping concentration;the light dark current suppression ratio of TiO₂:BiClO-2 device is6.12×10² at 300 nm,which is 6 times higher than that of TiO₂ device.In the third chapter,the photocurrent,responsivity of TiO₂:BiClO composite film detector and TiO₂ detector are compared in detail.In this paper,two kinds of wide-gap ultraviolet detectors based on built-in electric field effect were developed.By constructing local built-in electric field in TiO₂ film,the performance of the device in dark state and under ultraviolet light was effectively improved,and the performance parameters such as dark current,responsiveness and detection sensitivity of the device were improved.This paper provides valuable reference for the selection of doping materials,structural design and device working mechanism analysis of TiO₂ wide bandgap semiconductor uv photodetector.