Deep-ultraviolet Photodetector And Image Sensor Based On ?-Ga₂O₃

Solar-blind deep-ultraviolet?DUV?photodetectors operating in the waveband of 200-280 nm have received ever growing attention because of their vast applications for many military and civil purposes including missile warning,secure space-to-space communication,flame detection,remote control,and chemical and biological analysis.Ultrawide-bandgap?UWBG?semiconductors with appropriate bandgaps are very suitable for constructing solar-blind DUV photodetectors.Many studies reveal that monoclinic Ga₂O₃??-Ga₂O₃?,as one of the UWBG semiconductors,is the most stable form of Ga₂O₃,and has a direct bandgap in the range of 4.4-5.3 e V.This material can easily be synthesized via many methods.The above merits render?-Ga₂O₃ one of the most promising candidates for fabricating high-performance solar-blind DUV photodetectors.However,metal catalysts are normally required for growing high-quality?-Ga₂O₃nanowires,which inveitably introduces impurities,limiting device performance.In addition,patterning of?-Ga₂O₃ thin films,which can efficiently reduce crosstalk between adjacent devices,is an essential technique for device integration towards practical applications.Nevertheless,it is rather hard to pre-pattern the?-Ga₂O₃ thin films via photolithography due to high-temperature required for synthesizing the material with high-quality.Patterning of?-Ga₂O₃ thin films through other techniques such as etching is also very difficult.The above circustances greatly hinder the preparation of high-quality?-Ga₂O₃ and the development of?-Ga₂O₃-based optoelectronic integrated devices.In this thesis,a vapor-solid synthesis technique for catalyst-free growth of single-crystalline?-Ga₂O₃ nanowires is firstly developed.A photodetector composed of the nanowires exhibits a high sensitive to 265 nm DUV light illumination.The I_light/I_dark,responsivity,specific detectivity and response time can reach?10³,?233 AW^-1,?8.16×10¹² Jones,and 0.48/0.04 s,respectively.The nanowire-based photodetector can also serve as a DUV image sensor with good imaging function and decent spatial resolution.In addition,another technique combing the processes of photolithography and thermal-assisted conversion is also developed to realize patterned growth of?-Ga₂O₃ thin films in a large-scale.Based on such a technique,we construct a?-Ga₂O₃ thin film-based photodetectors array comprising 8×8 device units.The devices possess a ultra-low dark 10 V,the peak responsivity at 265 nm attains?0.72 AW^-1.Additionally,the 64 device units display excellent uniformity in photoresponse performance,which enables the huge potential in DUV imaging application.The results reveal that the catalyst-free grown?-Ga₂O₃ nanowires and patterned grown?-Ga₂O₃ thin films presented in this thesis hold excellent optoelectronic propreties.The photodetectors based on these materials also display outstanding DUV photoresponse performance,and can be applied in DUV imaging applications.It is believed that our work is helpful for developing low-cost high-performance solar-blind DUV photodetectors and image sensors,as well as promoting the integration of solar-blind DUV photodetectors.