Study On Gallium Oxide Material And Solar Blind Ultraviolet Detector

Gallium oxide(Ga₂O₃)is a new wide band gap transparent conducting semiconductor with five known polymorphs.Because of its 4.4?5.3e V wide bandgap,high breakdown field strength,large Baliga's figure of merit value,gas sensing characteristics,ultraviolet(UV)response characteristics,excellent thermal stability and chemical stability,Ga₂O₃ is widely used in the fields of gas sensors,solar blind UV photodetectors,high power electronic devices.Due to the limited size and high price of the Ga₂O₃ homogeneous substrate,it is great important for the study of high quality Ga₂O₃ heteroepitaxy films.In particular,Ga₂O₃ nanowires play an important role in the integration of heterogeneous devices and the development of new structures due to its high surface volume ratio,quasi-one-dimensional structure and two-dimensional stress release characteristics.In this paper,heteroepitaxy epitaxy of Ga₂O₃ material and its UV photodetector(PD)were studied.The main contents are as follows:1.Heteroepitaxial?-Ga₂O₃ films were prepared on c-plane sapphire substrate by MOCVD.The effect of film thickness on the properties of?-Ga₂O₃ film was studied.With the increase of the film thickness,the crystal quality of the films was improved.The minimum FWHM of 0.46°was obtained at 480nm-thick.With the increase of film thickness,the dislocation decreased and the crystal quality tended to be stable indicated by TEM.And it is verified that c-plane sapphire and?-Ga₂O₃ have an epitaxy relationship of Al₂O₃(11(?)0)??-Ga₂O₃(10(?)0).The ohmic contact UV PD based on the 480nm-thick Ga₂O₃ film exhibited high light-dark current ratio(2×10³)and high response peak(146 A/W)at 5 V bias.2.In order to improve the photoelectric performance of the film PD with traditional structure,the mechanism of self-reactive corrosion between Ga and Ga₂O₃was used to study the preparation of Ga₂O₃nanopore film by MOCVD.It was found that when the flow rate of TEGa flow rate in the corrosion process was the same as that of pre deposited TEGa,Ga₂O₃ nanopore film with better corrosion effect could be prepared on the unannealed film.Based on Ga₂O₃ film and nanopore film,Schottky contact solar blind UV PDs was prepared,respectively.The results showed that the light-dark current ratio of the nanopore film photodetector was 2.5×10² times that of the film PD,and the peak responsibility was 45 times that of the film PD.In order to reduce the influence of the surface state of the nanopore film,a 50nm SiO₂ layer was deposited on the nanopore film to prepare PD.The results showed that the peak responsibility of the PD was 5 times of that of the PD without the surface dielectric layer,and the photoelectric response performance of the device was further improved.3.?-Ga₂O₃ nanowire arrays were fabricated on GaN substrate by MOCVD.The regulation of the catalyst deposition process was studied,and a simplified catalyst combination model was proposed based on the principle of reduced cluster mobility.The design of SiO₂ mask with ordered nanopore array was studied.Through the function of the mask diffusion barrier,by adjusting the deposition time and annealing temperature of the catalyst,the ordered array of?-Ga₂O₃ nanowires with high vertical ratio,high filling rate and controllable diameter on GaN substrate was successfully prepared.4.Finally,preliminary explorations were explored on the process of?-Ga₂O₃nanowire array/GaN broadband UV PD.Based on the comparative study of the flattening methods of nanowire array,a method of fabricating double-layer mask based on SiN and SiO₂ was proposed.The fabrication process of?-Ga₂O₃ nanowire array/GaN broadband UV PD based on double-layer mask is designed,and the preliminary exploration experiment was carried out to verify the feasibility of the process.