Characteristic Study Of Solar Blind Ultraviolet Detector Based On Ga₂O₃ Single Crystal

As a direct bandgap semiconductor material,Ga₂O₃ has received extensive attention in recent years.With bandgap of 4.9 eV,and the corresponding cutoff wavelength of the ultraviolet detector based on Ga₂O₃ exactly locates in the solar-blind spectral region.In addition,Ga2O3 has the advantages of large light absorption coefficient and high chemical stability,makes it an ideal semiconductor material for fabricating the solar-blind ultraviolet?UV?detector.In this paper,SBD-based and MSM-based solar-blind UV detectors were fabricated using the?-Ga₂O₃ single crystal.The characteristics of the two types of detectors were tested and analyzed,respectively.The specific content of this paper is as follows:1.The X-ray diffraction analysis and the UV transmittance test of the?-Ga₂O₃ single crystal material used for the development of the detectors showed that the single crystal material has good crystal quality and excellent UV transmittance.A self-powered solar-blind UV photodetector was complished based on Pt-Ga₂O₃-Ti/Au Schottky junction.The I-V characteristic shows that the detectors have excellent deep UV response characteristics with the light to dark ratio of about 10⁴ under zero voltage bias.The time response perfromance shows that the detector has a fast response speed with the rise and decay times are 65 ms and 15 ms respectively,which further confirms the self-power supply capability of the detectors.The response time is gradually increased at a larger fixed voltage,showing a significant persistent photoconductivity?PPC?.This is due to the oxygen vacancies present in the Ga₂O₃ single crystal are gradually released by the applied electric field after the voltage is applied.When the light source is turned off,these photocarriers are still collected by the electrodes to generate loop current.Finally,the working mechanism of the self-powered SBD type solar-blind ultraviolet detector is explained by understanding of the movement of photo-generated carriers.2.MSM structure solar-blind UV detectors were carried out by the conventional photolithography process,and the following characteristics were mainly studied:?1?The performance of detectors based on high-resistance and low-resistance single crystal was compared and analyzed.The results show that compared with the I-V curve of high-resistance detectors,the carrier concentration of low-resistance materials participating in transport is higher.Therefore,the photocurrent of the low-resistance detector is significantly higher by an order of magnitude.However,the dark current is also greatly increased,resulting in a reduction in the current ratio.At a voltage of 0-10 V,the current ratio of the high resistance sample is maintained above 10³,and the maximum value of2.2×10⁶ is obtained at 3.1 V.While the low resistance sample has a current ratio of only 10²and a maximum of 6220?0.4 V?.?2?The effect of the interdigitated pattern of the electrodes on the performance of the detector was investigated.The study found that:a.thinner and denser interdigital electrodes can improve the photocarriers collection efficiency of the electrode,thereby improving the photocurrent of the detector and improving the performance of the device.b.The effective ultraviolet light receiving area is strongly correlated with the photocurrent.The larger the area,the larger the photocurrent.The performance of the device is limited by the length and width of the interdigital electrodes.The magnitude of the photocurrent depends mainly on the area of the effective absorption area of the ultraviolet light.?3?In order to improve the performance of the MSM solar-blind detectors,the electrodes were fabricated using the semi-transparent Pt/ITO composite structure electrode.The results show that the photocurrent of the Pt/ITO composite electrodes can reach 10^-310^-2A.Compared with the single-layer Pt electrode,the photocurrent is improved by 4 orders of magnitude,without reduction of the light-dark-curret-ratio,indicating the advantage of Pt/ITO composite electrode on Ga2O3 MSM ultraviolet detector.