Effect Of Doping On The Performance Of Gallium Oxide Ultraviolet Photodetector

Gallium oxide?Ga₂O₃?,as a wide bandgap semiconductor material,has attracted wide attention of researchers due to its large band gap?4.9 eV?and stable physicochemical properties.In recent years,gallium oxide has been widely used in various device applications,such as solar blind UV detection,gas detection and power devices.Metal-semiconductor-metal?MSM?structures are widely used in solar blind UV photodetector?PD?due to their large light-receiving area and simple preparation process.However,there are still great challenges in preparing Ga₂O₃-based solar blind UV detectors which has high-response and high-sensitivity.In this work,two methods were used to prepare high-performance Ga₂O₃-based solar-blind UV PD.First,Sn-doped Ga₂O₃ thin film was used to improve responsivity of the PD.Second,(In_xGa_1-x)₂O₃ based sandwich structure UV photodetector was fabricated to improve sensitivity and specific detectivity of solar-blind PD.The details are as follows:?1?This paper studied the effect of substrate temperature on Sn-doped gallium oxide thin films.Results show substrate temperature of 560°C is an optimized epitaxial growth parameter for Sn-doped Ga₂O₃.Photocurrent and dark current of the solar blind UV detector prepared at a substrate temperature of 560°C were much larger than those films grown at higher temperature.On this basis,this paper studied the effect of Sn source temperature on performance of Sn doped Ga₂O₃ solar-blind PD.Sn-doped epitaxial film were grown at a substrate temperature of 560°C and Sn source temperature of 750,850,and 900°C,respectively.Results show that the photocurrent and dark currents of the Sn-doped Ga₂O₃ solar ultraviolet PDs increased with increasing Sn source temperature.This is mainly due to the increase of the carrier concentration by Sn doping,which lowers the resistivity of the film,thereby greatly increasing the responsivity of the device.However,as the temperature of Sn source raised to 1000 and1100°C,the crystal quality of the gallium oxide film were gradually deteriorated,and photocurrent,dark current and responsivity of the device gradually decreased.These result indicate excessive temperature of Sn cause the deteriorates of crystal quality,resulting in deterioration of the performance of the PDs.Above all,films with substrate temperature of 560?and Sn source of 900?exhibits the highest responsivity of444.51 A/W,indicating Sn doping can effectively improve the performance of Ga₂O₃PDs.?2?In this paper,a Ga₂O₃-(In_xGa_1-x)₂O₃-Ga₂O₃ sandwich structure solar-blind PD was developed.Since In can adjust the band gap of Ga₂O₃,and increase the mobility of the film,(In_xGa_1-x)₂O₃ is very suitable for the preparation of high-performance PDs.Results show that with the increase of the thickness of the top Ga₂O₃ layer,the dark current of the sandwich structure PD was significantly reduced,which greatly increased the special detictivity and sensitivity of the device.The reduction of dark current is attribute to the introduction of top Ga₂O₃ layer which changes the contact characteristics between metal and(In_xGa_1-x)₂O₃ film,which optimized device performance.The specific detectivity of PD with 15 nm top Ga₂O₃ layer is 3.06×10¹³ cm·Hz^1/2/W,which increased by an order of magnitude than that of Ga₂O₃-(In_xGa_1-x)₂O₃ structure,indicating that(In_xGa_1-x)₂O₃ sandwich structure can optimize the photocurrent and dark current of the solar blind UV PD and improve the specific detectivity of the device,thus improving the performance of the solar-blind PD.