Preparation And Photoelectric Detection Properties Of Solar-blind Ultra-violet Detectors Based On β-Ga₂O₃ Thin Films By Radio Frequency Magnetron Sputtering

β-Ga₂O₃ belongs to typical ultra-wide band gap semiconductor material with band gap of4.9e V.Owing to a high critical electric field strength（8MV/cm）and outstanding thermal and chemical stability,it has broad application prospects in the fields of photodetectors,sensors and high-power electronic devices.In this thesis,β-Ga₂O₃ thin films with different parameter was prepared on the sapphire（001）substrate by radio frequency magnetron sputtering technology at room temperature,and then annealed in different atmospheres at different annealing temperatures.The effect of thin film thickness,annealing atmosphere and temperature on the obtainedβ-Ga₂O₃ thin films were systematically investigated.Furthermore,the MSM solar-blind ultraviolet photodetector was prepared based on theβ-Ga₂O₃ thin films and the photoelectric detection properties were explored in depth.The main results are as follows:（1）Using radio frequency magnetron sputtering,β-Ga₂O₃ thin films with the thickness in the range of～210-1050 nm were prepared on a sapphire（001）substrate by regulating the deposition time.It was found that,as the thin film thickness increases,the crystallinity of the obtainedβ-Ga₂O₃ thin films first increases,and then declines a little.All the prepared thin films have obvious UV absorption characteristics,and the band gap width increases with the increase of thickness.The photoluminescence（PL）spectrum results of the thin film show that the peak intensity of each luminescence peak decreases with the increase of thin film thickness.The photoelectric detection properties of the devices show the law of first increasing and then decreasing with the increase of thickness.The thickness of 840nmβ-Ga₂O₃ ultraviolet photodetector shows extremely low dark current(4.9×10^-12A),extremely short response time,and its photo-dark current ratio is as high as 3.2×10~5,its responsivity,detectivity and EQE are1.19m A/W,1.9×10¹¹ Jones and 0.58%respectively.（2）The high-qualityβ-Ga₂O₃ thin films with thickness of～840nm were placed in a high-temperature tubular horizontal furnace with different annealing atmospheres（argon and oxygen）for annealing.The annealed samples were compared with the unannealed sample.It was found that annealing in an oxygen atmosphere has a greater enhancement in the crystalline quality of the thin films.As for the detector fabricated using the thin film annealed in an oxygen atmosphere,under 254nm ultraviolet light and a bias of 5 V,the response time is the shortest,the rise time is 0.08s/0.75s,the fall time is 0.05s/0.48s,and the device properties is better.Thus,it can be concluded that the annealing atmosphere had a great influence on the quality of the thin film and the properties of the device.（3）By changing the annealing temperature of theβ-Ga₂O₃ thin film（400-1000℃）,the effects of annealing temperatures on the crystal structure,optical properties of the thin film and the photoelectric detection properties of the devices were explored.The results show thatβ-Ga₂O₃ thin films at different annealing temperatures have ultraviolet light absorption in the range of 200 to 300 nm obviously.As the annealing temperature increases,the optical absorption edge appears blue shift,and the band gap of the thin film also increases.The PL spectrum results show that the annealing temperature of 1000°C has a greater impact on the oxygen vacancy defect concentration of the thin film.While the annealing temperature of600°C has a greater impact on the concentration of oxygen vacancy defects and gallium-oxygen vacancy defects in the thin film.All the devices with different annealing temperatures have fast response speed.As the annealing temperature increases,the response time（rise time and fall time）of the device first increases and then decreases.The device annealed at 800°C has the best photoelectric detection properties.As the annealing temperature increases,the photo-dark current ratio of the device first increases and then decreases.The photo-dark current ratio of device T3（annealed at 800°C）is the largest,up to 2.0×10~4.The T3 device can operate in a dynamic region,giving the device a higher applied bias voltage or optical power density,it can lead to higher photocurrent.