Study On Solar-blind Photodetectors Of Gallium Oxide/Aluminum Nitride Heterojunction

Because of the strong absorption and scattering of the atmosphere,sunlight with wavelengths shorter than 280 nm cannot reach the surface of the earth.This wavelength region is called the solar blind ultraviolet region,which provides a low background window for optical detection.The photodetectors working in the solar blind ultraviolet region have the advantages of low false alarm rate and high signal-to-noise ratio,thus have broad application in many fields,such as remote control,space security communications,missile early warning,and flame detection.Ultra-wide bandgap semiconductors are utilized to fabricate solar-blind photodetectors,including AlN,Mg Zn O,diamond,Al Ga N,and gallium oxide（Ga₂O₃）.Among them,Ga₂O₃ has a bandgap of 4.5-4.9 e V,which covers most of the solar-blind UV region,avoiding relatively complicated band regulation engineering.Moreover,Ga₂O₃ has the advantages of good chemical stability,high thermal stability,and high breakdown electric field.Therefore,Ga₂O₃ is suitable for solar-blind detection.However,the response times of Ga₂O₃ solar-blind photodetectors are usually milliseconds or seconds,which severely limits their practical applications.To improve the respone speed of Ga₂O₃ photodetectors,this paper constructs a high-quality Ga₂O₃/AlN heterojunction,which utilizes the built-in electric field in the heterojunction to promote the separation and collection of photogenerated carriers.Thus,the device can work at zero bias with a faster response speed.We prepared Ga₂O₃/AlN heterojunction solar-blind ultraviolet phtodetectors by plasma enhanced chemical vapor deposition（PECVD）and magnetron sputtering.And studied the photon response characteristics.The main research content and results are as follows:The Ga₂O₃/AlN heterojunction photodetectors can work without an external bias.The device shows a response peak of 242 nm with a cut-off wavelength of 260 nm and an UV/visible rejection ratio of 2.2×10³.The Ga₂O₃/AlN heterojunction photodetector also has a responsivity of 7.0 m A/W at zero bias,a detectivity of 1.25×10¹³cm·Hz^1/2·W^-1,and an ultra-fast response time of 320 ns,which are among the best values of Ga₂O₃ photodetectors working at 0 V.The results of this study show that Ga₂O₃/AlN heterojunction may be a promising way towards solar-blind detectors with high sensitivity and fast response speed.