Investigations Of Gallium Oxide Based Films And Solar Blind Ultraviolet Array Sensor

With the development of science and technology,semiconductors with wide band-gap behave great advantage in semiconductor lighting,power devices and UV electronic devices etc.for their lower energy consumption,higher electron saturation rates and lower energy loss.Among them,gallium oxide,exhibiting a native n-type wide bandgap semiconductor,has also received great attention in recent years.With a band gap of?4.9 eV(corresponding to an absorption edge of?270 nm),Ga2O3 exhibits obvious photoresponse to the radiation in solar-blind region,leading to a promising candidate of solar-blind photodetectors(PDs).As research continues,Ga2O3 based PDs are expected to apply in the fields of solar-blind imaging,telemetry,optical positioning and so on,thus the multi-pixel,integrated and miniaturized gallium oxide sensor array is gradually becoming a research hotspot.However,the research on gallium oxide PDs array are still in the initial stage.Therefore,we focus on the investigation of the PDs array in this paper.We deposited Ga2O3 films through metal organic chemical vapor deposition(MOCVD)and pulsed laser deposition(PLD)methods,and prepared PDs array with different structures by standard photolithography process,and investigate the properties of the devices subsequently.The detailed works are listed as follows:(1)Non-intentionally doped gallium oxide films and Si-doped Ga2O3 films are deposited on sapphire substrate,and the photoelectric performance of the devices are tested subsequently.Through the measurement,the pure gallium oxide films behave fast response speed(?d-38 ms),good linearity and moderate response(about 17 A/W under 10 V),while the Si-doped Ga2O3 films exhibit large photocurrent,a proper response speed,and a good linear relationship.In addition,we also deposited Sn-doped Ga2O3 films by PLD methods and investigated the effect of growth conditions on crystal structure and surface morphology.From the XRD results,it could be deduced that the crystalline phase changes as the law of ???+???with the increasing of the tin concentration.Furthermore,it is also found that the film roughness changes smaller with the introducing of oxygen atmosphere.Thereby,Sn-doped Ga2O3 films deposited under oxygen atmosphere is more suitable for the subsequent fabrication of PDs array compared with Sn-doped Ga2O3 films deposited under vacuum condition.(2)Solar-blind ultraviolet detector array with asymmetric interdigital electrode structure was fabricated on a two-inch Ga2O3 films,and the properties of the device are investigated.It could be found that the device has obvious response to UV irradiation at 254 nm,and the response rejection ratio of 254 nm/365 nm is about 104.Moreover,the device exhibits self-powered performance in the test.As the positive bias was applied to Au/Ga2O3 contact,the photodetector presents a responsivity of ? 0.3 A/W(10 V)and ultra-high photo to dark ratio(2×106?9×107).However,the device exhibits faster response time(?d=50 ms)under 0 V bias.Further analysis revealed that the self-powered behaviors may attribute to the separation and driving effect on the non-equilibrium carriers by the built-in electric field in the Schottky junction.(3)One-dimensional linear Ga2O3 photodetector array was designed and prepared by lift off process,and the photoelectric performance of the device was studied.From the results,it could be found that the device exhibits high photo to dark ratio(3,06 ×107),high photoresponsivity(243.66 A/W)and short response time(0.05 s).In addition,by measuring the behaviors of all the PDs cell in the linear detector,it is shown that the behaviors of each photodetector unit in the PDs array have good uniformity.(4)The design of array detector structure and the corresponding photolithography process are explored,and the material selection of junction structured array detector is also studied.Two kinds of multipixel array detectors with two electrode structures(symmetrical and asymmetrical interdigital fingers)were designed and fabricated,and the related photoelectric properties of the devices were investigated.Subsequently,BaTiO3/Ga2O3 and In2O3/Ga2O3 hetero-junctions were prepared using the PLD method,and the band alignments of these two hetero-junction are calculated.Through the Kraut's method,we found that both BaTiO3/Ga2O3 and In2O3/Ga2O3 heterojunctions exhibit Type-I alignments,which indicates that BaTiO3 and In2O3 are certified as excellent materials to inject electrons into Ga2O3,and may well be beneficial to the contact resistance reduction,for Ga2O3,as an interlayer between metals and Ga2O3.