Preparation And Study Of ?-Ga₂O₃ Thin Films

As an emerging third-generation semiconductor material,?-Ga₂O₃has broad application prospects in the fields of power devices,solar-blind ultraviolet detectors,and transparent conductive films due to its excellent physical,chemical,and optoelectronic properties.High-quality thin films is the basis for the preparation of high-efficiency Ga₂O₃-based devices.The preparation,characterization and photoelectric properties of?-Ga₂O₃thin films has profound significance.In this paper,the research on the preparation of?-Ga₂O₃polycrystalline films by RF magnetron sputtering deposition of?-Ga₂O₃amorphous film and ex-situ annealing in a horizontal tube type high temperature diffusion furnace is carried out by using C-plane sapphire(Al₂O₃)as the substrate.For?-Ga₂O₃polycrystalline films prepared under different process conditions,use X-ray diffractometer(XRD),atomic force microscope(AFM),scanning electron microscope(SEM),Hall tester and integrating sphere spectrophotometer to analyze and study the crystalline properties,surface morphology,and photoelectric properties of the film.The main work and results achieved in this paper are as follows:(1)The effect of RF magnetron sputtering process on the quality of?-Ga₂O₃polycrystalline films was studied.Use the radio frequency magnetron sputtering method,by changing the substrate temperature,oxygen and argon ratio,working pressure,sputtering power and deposition time,deposit?-Ga₂O₃amorphous films with different process conditions,and then use the same ex-situ annealing process to obtain?-Ga₂O₃polycrystalline films.The effects of different RF magnetron sputtering process parameters on the crystalline properties,surface morphology,and deposition rate of the films were analyzed by using XRD,SEM,AFM and other characterization methods.The optimized?-Ga₂O₃thin films RF magnetron sputtering deposition parameters are:substrate temperature 500?,oxygen flow rate 2.3sccm,argon gas flow rate 46.2sccm,working pressure 1.0Pa,sputtering power 150W and deposition time 90min.(2)Further study the effect of ex-situ annealing process on the quality of?-Ga₂O₃thin films.The optimum magnetron sputtering process was used to deposit the Ga₂O₃amorphous films,the process parameters of heterotopic annealing were changed:annealing temperature600?1100?,annealing atmosphere of oxygen and nitrogen,annealing time 60?180min,different properties can be prepared?-Ga₂O₃polycrystalline films.By using XRD and AFM testing methods,analyze and study the effects of different ex-situ annealing processes on the crystalline properties and surface morphology of?-Ga₂O₃thin films:poper annealing temperature can drive the thin films to recrystallize,and the crystallization performance is significantly improved.If the annealing temperature is too high,the crystal structure of the thin films will be damaged,and the preferred orientation will become worse;Compared with the nitrogen annealing atmosphere,the oxygen atmosphere can eliminate the oxygen vacancies in the thin films and improve the surface morphology of the thin films;Properly extending the annealing time,the atoms inside the thin films have enough energy to move to the proper position of the lattice,which is beneficial to improve the properties of the thin films.The optimized preparation process parameters of?-Ga₂O₃polycrystalline film are:substrate temperature 500?,oxygen flow rate 2.3sccm,argon gas flow rate 46.2sccm,working pressure 1.0Pa,sputtering power 150W,deposition time 90min,annealing temperature 1000?,oxygen annealing atmosphere,annealing time 90min.(3)The effects of various process parameters of RF magnetron sputtering and ex-situ annealing on the optical and electrical properties of?-Ga₂O₃polycrystalline films are studied.The absorption spectrum of the?-Ga₂O₃thin films was measured with an integrating sphere spectrophotometer.The test results shows that the light absorption intensity of the thin films absorption spectrum under different preparation process conditions changed with the increase of wavelength in the same trend:the whole trend first increases,then decreases,then increases,and finally decreases.Two light absorption peaks appear near the wavelengths of 240nm and300nm,and the first absorption peak has a strong intensity.The?-Ga₂O₃thin films has good light absorption characteristics in the deep ultraviolet region.Changing the thin films preparation process parameters will affect the light absorption intensity of the film absorption spectrum:the substrate temperature rises,and the absorption characteristics of the?-Ga₂O₃thin films deteriorate;the film prepared at a lower oxygen flow rate shows better optical properties;the working pressure has an effect on the light absorption intensity of the thin films absorption spectrum,and the thin films prepared under the conditions of 1.0Pa and3.0Pa have better UV absorption characteristics;the higher the sputtering power,the better the optical properties of?-Ga₂O₃thin films;The optical properties of the thin films prepared under the conditions of deposition time of 90min and 120min are better;The ultraviolet absorption effect of the thin films is better when the annealing temperature is 900?and1000?;the absorption characteristics of the thin films treated in an oxygen annealing atmosphere are obviously better than that in a nitrogen atmosphere;the optical properties of the films annealed for 60min and 180min are better.Hall effect measurement results show that?-Ga₂O₃thin films exhibits weak n-type conductivity,and changes in process parameters will not affect the conductivity type of the thin films.But it will have a certain impact on electrical parameters such as Hall mobility,carrier concentration,and resistivity of the thin films.