Preparation And Performance Optimization Of Si-based Ga₂O₃ Heterojunction Solar Blind UV Photodetector

In recent years,the third generation semiconductors represented by gallium nitride(GaN),silicon carbide(SiC)and zinc oxide(ZnO)have been fully developed.Among them,gallium oxide(Ga2O3),as an ultrawide band semiconductor material,has attracted a lot of attention from researchers with its advantages of good thermal stability,large band width,large UV absorption coefficient and high chemical stability.The band gap of gallium oxide varies with its crystal structure and is roughly in the range of 4.2～5.3 eV.When solar radiation passes through the atmosphere,the ozone layer in the atmosphere has a strong absorption effect on 200～280 nm UV radiation,and the UV radiation in this band is almost non-existent in the near-Earth atmosphere,because the solar radiation in this band region(200～280 nm)is basically zero in the atmosphere,especially in the atmosphere near sea level,so this band is not affected by solar radiation and becomes a solar-blind region.The forbidden band width of Ga2O3 can cover the day-blind band well,so Ga2O3 is the preferred material for preparing day-blind UV photodetectors.In this work,p-Si is chosen as a heterogeneous material to form a heterojunction with gallium oxide.The Ga2O3-based heterojunction solarblind UV photodetector is prepared,and the structure of the device is optimized on this basis to improve the optoelectronic performance of the device.The main work and research results of this paper are as follows:(1)Ga2O3 thin films were prepared using metal organic chemical vapor deposition technique and Ti/Au metal electrodes are prepared using magnetron sputtering technique.The p-Si/Ga2O3 heterojunction photodetector and p-Si/SiO2/Ga2O3 PIN junction photodetector are prepared,respectively.(2)The p-Si/Ga2O3 heterojunction photodetector and the pSi/SiO2/Ga2O3 PIN junction photodetector are tested in detail for their optoelectronic performance.Due to the insertion of the SiO2 dielectric layer,the dark current of the p-Si/SiO2/Ga2O3 PIN-junction photodetector is substantially reduced to 1.14×10-12 A at a bias voltage of-15 V,which is four orders of magnitude lower than that of the p-Si/Ga2O3 heterojunction photodetector(3.22×10-8 A).At the same time,the light-to-dark ratio of the PIN junction photodetector has also improved substantially,reaching 1.81×105 under the UV illumination of 920 μW/cm2,which is three orders of magnitude larger than that of the p-Si/Ga2O3 heterojunction photodetector at 2.6×102.Other photovoltaic performance parameters such as responsivity,external quantum efficiency,detection rate and response time of the PIN junction photodetector are much higher than that of the pSi/Ga2O3 heterojunction photodetector.The other photodetector parameters such as responsivity,external quantum efficiency,detectivity and response time of PIN junction photodetector are superior to p-Si/Ga2O3 heterojunction photodetector.In addition,both the fabricated photodetectors exhibit excellent stability and are able to operate continuously for a long time in the same environment.The results of this thesis show that with the insertion of the SiO2 dielectric layer,the detection performance of the p-Si/SiO2/Ga2O3 PIN junction photodetector is substantially improved compared with that of the p-Si/Ga2O3 heterojunction photodetector,which has great potential for high sensitivity and ultra-fast response in the field of solar-blind UV photodetection.