UV-vis Photodetectors Based On Ternary Metal Oxide Semiconductor

Photodetectors are widely used in production and life due to their unique light-to-electrical signal conversion capability.Among them,silicon-based photodetectors were the first to be commercialized due to their mature process and excellent optoelectronic performance.However,silicon-based photodetectors still suffer from high leakage current,which leads to high static power consumption and difficulty in overcoming environmental noise,thus greatly limiting the application of silicon-based photodetectors in complex environments.To address these issues,this thesis proposes a new type of heterojunction photodetector using a metal oxide semiconductor as a functional layer with a silicon substrate.In this paper,two ternary metal oxide semiconductor materials,copper bismuthate(Cu Bi₂O₄,or CBO)and bismuth iron oxide(Bi Fe O₃,or BFO),will be used to investigate this silicon-based heterojunction photodetector,with the main findings being.(1)n-Si/p-CBO photodetectors were prepared by depositing p-type CBO films on the surface of n-type Si using spin-coating method.The detector has an extremely low dark current of?2×10^-11A,excellent self-powered characteristics with an optical voltage of?0.55 V,a high switching ratio of 1.69×10~4at zero bias,and ultra-fast time response with rise and fall times of?0.1 and 0.3 ms.These characteristics enable the device to perform well in high-speed optical response systems.The positive correlation between device performance and film thickness suggests that the top oxide semiconductor acts as the light harvesting layer,generating,separating and transmitting photogenerated carriers through the built-in heterojunction,thus enabling the conversion of optoelectronic signals.Energy band analysis further confirms these findings and reveals the transport of photogenerated carriers between heterojunctions:photogenerated electrons are transferred from CBO to Si,while photogenerated holes are transferred from Si to CBO.(2)To verify the universality of the above device structure,n-Si/p-BFO photodetectors were prepared by depositing p-type BFO films on the n-type Si surface using spin-coating.n-Si/p-BFO photodetectors also exhibit excellent performance:dark current of?0.15 n A;high switching ratio of?8×10~4at zero bias;peak wavelength at 550 nm with high responsivity of?25.2 m A·W^-1and a detecitivity of?3.22×10¹¹Jones(cm·Hz^1/2·W^-1,referred to as Jones).This thesis addresses the problems of high leakage current,poor interference immunity and high static power consumption of conventional silicon-based photodetectors,and proposes the use of metal oxide semiconductors as the top functional layer to form a novel heterojunction photodetector with a silicon substrate.Two research works have shown that the new device can effectively reduce the leakage current and improve the responsiveness,detection rate and response speed of the silicon-based self-powered photodetector.This thesis provides a new material choice and an effective device design strategy for building silicon-based heterojunction photodetectors.