| In recent years,the new generation of semiconductor material gallium oxide(Ga2O3)has gained widespread attention due to its advantages such as a wide bandgap of 4.9 eV and lowcost single crystal substrate growth methods,and research on its optoelectronic detection has been emerging.However,due to its ultra-wide bandgap,research has mainly focused on the near-ultraviolet band,and its application range is limited.In this paper,two types of photodetectors based on β-Ga2O3 single crystal substrate and Schottky diode structure formed with Au were designed and prepared,respectively,to work in the near-ultraviolet to visible light band and the day-blind ultraviolet band,and their characteristics were tested and analyzed.The specific contents of the paper are as follows:Ⅰ.Design and preparation of a hot-electron photodetector based on β-Ga2O3 single crystal substrate,including:1.Designed two types of periodic nanohole array structures based on β-Ga2O3 single crystal substrate and Au thin film,which can achieve broadband high absorption and selective absorption in the ultraviolet-visible light band.The light absorption mechanism was analyzed,and the structure design was optimized according to these mechanisms.2.Focused ion beam(FIB)technology was used to etch periodic nanohole arrays on Sndoped β-Ga2O3 single crystal substrate,and a hot-electron photodetector based on Au-Ga2O3 Schottky barrier diode was prepared by combining photolithography,evaporation,and other micro-nano processing technologies.The photoelectric response of the device was tested,and the photoelectric current response from 300 nm to 600 nm was achieved by using the hot electrons generated by interband absorption of Au.The response current of 405 nm laser is proportional to the optical power.By increasing the reverse bias of the device,the transition efficiency of hot electrons was improved,and higher photoelectric response was obtained.3.The theoretical quantum efficiency of the device was analyzed and calculated from the perspective of the generation,transmission,and emission of hot electrons.It was found that in the band where the photon energy is greater than 2 eV,the theoretical quantum efficiency of the device is lower than the traditional hot electron emission theory quantum efficiency due to the interband absorption of Au.The calculation and analysis of the hot electron emission theory can help design more efficient hot electron devices.Ⅱ.Design and preparation of a UV photodetector based on Au-Ga2O3 Schottky barrier diode.Through electrical testing,the Schottky barrier height of the device was found to be about Φb=1.02 eV,the carrier concentration Nd of β-Ga2O3 single crystal substrate without intentional doping was about 8.2×1016/cm3,and the built-in potential qVbi was about 0.95 eV.Under 0 bias voltage,the depletion layer width was about 112 nm.By setting a 10 nm Au electrode,the transmission rate of the UV light was ensured,so that it could be absorbed in the depletion layer inside the gallium oxide.When self-powered,the peak response of the device to 236 nm UV light was about 0.014 A/W;when the reverse bias increased to-10 V,the peak response of the device increased to 0.4 A/W,and the response peak position shifted to 248 nm,which may be due to the influence of bias on its energy band structure. |
