Research On The Fabrication And Performance Enhancement Of Amorphous Gallium Oxide Phototransistor

Solar-blind ultraviolet photodetectors have broad application prospects in fire warning,confidential communication,missile warning and other fields due to the unique advantage of low background noise.The emerging semiconductor material,gallium oxide,has an ultra-wide bandgap of～4.8 e V,making it naturally suitable for solar-blind ultraviolet detection.At present,research on gallium oxide generally focuses onβ-Ga₂O₃.In recent years,amorphous gallium oxide has appeared as an excellent photodetector with the ability to avoid high temperature processes,flexibly choose substrates,and low production costs,becoming a new research hotspot.The phototransistor can suppress the dark current and increase the photocurrent with gate voltage regulation,to obtain high detection sensitivity.However,amorphous gallium oxide films have low carrier mobility,making it difficult to achieve effective gate voltage control in the phototransistor.Therefore,this thesis aims to carry out preparation and performance studies of amorphous gallium oxide-based phototransistors to obtain stable and excellent device performance.Firstly,based on the MSM type device with uncomplicated process,the preparation process of amorphous gallium oxide films was initially explored.By adjusting sputtering power,substrate temperature,oxygen partial pressure,and sputtering time,the quality of amorphous gallium oxide films was optimized.Using AFM,XPS and other material characterization methods combined with related tests on the photoelectric performance of the device,the mechanism of the influence of different process parameters on the properties of the film was deeply analyzed,and the process parameters for the preparation of amorphous gallium oxide films suitable for photoelectric detection were obtained.At the same time,a MSM type photodetector with higher performance was prepared.Based on this,a back gated amorphous gallium oxide phototransistor was constructed,and effective gate voltage control was achieved.The detection performance was greatly improved compared to the MSM type device,for example,220.72 A/W of photocurrent responsivity and 3.57×10¹⁵ Jones of detectivity(the photocurrent responsivity and detectivity of MSM type devices were 2.14 A/W and 1.19×10¹⁴ Jones,respectively).Further research found that while appropriately increasing the oxygen partial pressure in the sputtering atmosphere can improve the transistor’s mobility,the detection sensitivity did not improve significantly at the expense of gain.Moreover,excessively high oxygen partial pressure can even lead to a decrease in mobility due to the sharp drop in carrier quantity.Therefore,single handedly adjusting the oxygen vacancy content in amorphous gallium oxide cannot continuously optimize the performance of phototransistors.Based on the above reasons,a device structure of a double layer amorphous gallium oxide homojunction was proposed,which includes a channel layer with oxygen-rich（high mobility）and a light absorbing layer with oxygen-poor（high gain）.The thickness distribution and process conditions of device were optimized.Finally,the mobility and subthreshold swing of the phototransistor were further optimized,and the transistor achieved excellent photodetection performance,such as 512.70 A/W of photocurrent responsivity,1.18×10¹⁶ Jones of detectivity,and 0.43 s/0.02 s of response speed.Through the above work,this thesis provides a method for preparing high quality amorphous gallium oxide films and successfully constructs a phototransistor with effective gate voltage control characteristics,achieving high detection sensitivity.Based on this,the double layer homojunction device structure proposed can further significantly optimize device performance.