Epitaxial Growth And Characterization Of Gallium Oxide Films Based On Mist-CVD

As a new type of ultra-wide band gap semiconductor,gallium oxide(Ga₂O₃)has a bright application prospect in power semiconductor devices and photodetectors,etc.Therefore,research on Ga₂O₃ material has been widely concerned by researchers at home and abroad.The most concerned Ga₂O₃ materials are?-Ga₂O₃ and?-Ga₂O₃.This paper focuses on the research of these two materials and adopts a low-cost mist chemical vapor deposition(Mist-CVD)system as the material growth method.In the studies on?-Ga₂O₃,the c-plane sapphire is usually used as the substrate material,while the studies on sapphire in other planes are very scarce.In this paper,by epitaxially growing?-Ga₂O₃ films on sapphire substrates with different crystal planes,through a series of material characterization methods,the differences of?-Ga₂O₃ films with different crystal planes are compared.In the study of?-Ga₂O₃ film,?-(Al_xGa_1-x)₂O₃ film was used as the intermediate layer,and the effect of adding the intermediate layer on the epitaxial growth of?-Ga₂O₃ film was studied.The main contents are as follows:1)?-Ga₂O₃ films were grown on a-plane,c-plane and r-plane sapphire substrates by Mist-CVD method,and a series of material characterization methods were used to determine the crystallinity,roughness,optical band gap,and growth rate of the samples.The lattice mismatch rate was also characterized.It was found that?-Ga₂O₃ films grown on a-plane,c-plane,and r-plane sapphire substrates have FWHMs of 0.204°,0.025°and1.115°,respectively,and c-plane?-Ga₂O₃ has the best crystallinity.The?-Ga₂O₃ film grown on c-plane sapphire substrate has a roughness of 1.64 nm and a band gap of 5.29 e V.In addition,using c-plane sapphire as the substrate has the fastest growth rate(11.44nm/min)and a relatively perfect lattice arrangement.These results prove that c-plane sapphire is the best substrate for?-Ga₂O₃ thin film growth.2)?-(Al_xGa_1-x)₂O₃ film was grown on c-plane sapphire substrates under different temperature by Mist-CVD method.XRD,UV-Vis and XPS were used to characterize the samples,it was found that the optimal temperature condition range for the growth of?-(Al_xGa_1-x)₂O₃ film is 850-900?,and the higher the temperature,the higher the aluminum composition in the film.3)The?-(Al_xGa_1-x)₂O₃ film grown at 900?was used as the intermediate buffer layer to epitaxially grow the?-Ga₂O₃ film,which was tested by XRD,XPS,AFM and UV-Vis to compare with the?-Ga₂O₃ film directly epitaxially on the c-plane sapphire substrate.The study found that after using?-(Al_xGa_1-x)₂O₃ film as the intermediate layer,?-Ga₂O₃ film has higher X-ray diffraction peak intensity,smaller FWHM(1.131°)and smaller RMS roughness(3.1 nm),proved that?-(Al_xGa_1-x)₂O₃ film as an intermediate layer can improve the lattice mismatch problem in the epitaxial growth of?-Ga₂O₃ film,thereby improving the quality of the film.