| Since the beginning of the 21st century,gallium oxide has been widely studied as a material for solar-blind ultraviolet detectors due to its band gap of 4.4-5.3 e V,stable chemical properties and mature preparation technology.In the research of improving the performance of photodetectors,reducing the dark current is very important.Lower dark current means less noise,greater signal-to-noise ratio and lower power consumption.In this paper,vertical Schottky detectors and planar MSM detectors are prepared on a gallium oxide single crystal substrate and film based on two interface control methods.The photoelectric characteristics of these photodetectors are tested to analyze the influence of these two interface control methods on the performance of gallium oxide ultraviolet detectors,and this study has a positive reference value for the development of gallium oxide ultraviolet detectors with lower dark current,higher contrast and faster response speed.The research work and results of this article are divided into two parts:1.The influence of surface Mg ion implantation process on the photoelectric performance of gallium oxide detectors was studied.Characterization tests were carried out on the substrate implanted with Mg ions,the substrate implanted with Mg ions but not annealed,and the substrate implanted with Mg ions and annealed,including XRD,UV-vis,Raman,PL and XPS tests.According to the results of these characterization tests,it can be found that the molecular structure near the surface was damaged and many defects were formed after the Ga2O3single crystal substrate was implanted with Mg ions.After annealing,the lattice ofβ-Ga2O3is repaired,and the implanted Mg ions enter the lattice,which increases the band gap of the Ga2O3single crystal substrate（the band gap of MgO is as high as 7.8e V）.Vertical Schottky detectors and planar MSM detectors were prepared on the above three substrates to test the photoelectric performance.The test results show that the surface Mg ion implantation process and the annealing process can bring a variety of performance improvements to the gallium oxide UV detector,including lower dark current(reduced from 10-11to 10-12under-10 V bias),a larger light-dark current ratio（an improvement from 112 to 1733）and better dynamic response characteristics（better cycle repeatability and 0.157/0.048 s rise/decay time）.2.The influence of the MgO high-resistance interface layer on the photoelectric performance of gallium oxide detectors is studied.First,the optimal growth conditions and annealing conditions for optimizing the quality of MgO films were studied.By characterizing MgO films prepared under various growth conditions,the optimal growth conditions of 60 W sputtering power,7 m Torr,and 1 sccm oxygen flow rate were finally determined.The best annealing conditions are determined to be slow annealing for two hours in a N2and 800℃environment.Ultraviolet detectors with MgO interface layer and without MgO interface layer were prepared on low-resistance gallium oxide single crystal substrate and gallium oxide film,respectively.The study found that the MgO interface layer effectively increased the barrier height of the interface.Due to the high resistivity characteristics of the MgO material,the depletion layer of the device was equivalently widened,which bringing a lower dark current and greater light-dark current ratio.The maximum light-dark current ratio of single crystal and film detectors has been increased by3 times and 5 times,respectively.Compared with devices without a MgO layer,the dark current of the vertical Schottky detector MgO layer under-5 V bias is reduced by three orders of magnitude from 10-2to 10-5,and the dark current of the planar MSM device with MgO layer is reduced by about 10 times under the bias voltage of 10 V. |
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