Preparation Of Ga₂O₃ By GaN Thermal Oxidation And Study On Their Ultraviolet Detectors

With the rapid development of science and technology in today’s society,various technologies are gradually pouring into human life and being used for various purposes in human society,such as military,civil,environmental,and so on.In the process of the rapid development of the third generation of semiconductors,namely broadband gap semiconductors,people’s demand for electronic components and the requirements for the detection environment are increasing.Wideband gap semiconductors（UWBGs）have a high voltage withstand range and stronger stability due to their large bandgap width,and are widely used in ultraviolet luminescence,ultraviolet lasers,ultraviolet detection,high-power high-frequency devices,and other fields.As a popular material in the field of ultraviolet photodetection,Ga₂O₃ has attracted widespread attention due to its ultra-wideband gap of 4.2 to 4.9 e V,high binding energy,high electron mobility,and other advantages.Various growth methods based on Ga₂O₃ thin films（MOCVD,PLD,MBE,magnetron sputtering,thermal oxidation）have been reported,among which thermal oxidation can effectively reduce the surface density of states and grow high-quality thin films.In this paper,Ga₂O₃ thin films have been successfully prepared by using Ga N thermal oxidation method,and Ga₂O₃/Ga N heterojunction devices have been constructed by wet etching.The specific research is as follows:（1）Preparation and characterization of Ga₂O₃ thin films.Mg-doped p-type Ga N thin films were grown using the MOCVD method.After that,high-quality Ga₂O₃ thin films were prepared by using high-temperature thermal oxidation of Ga N,controlling the oxidation temperature and gas flow rate.Subsequently,a series of characterization tests were carried out on Ga₂O₃ thin films.（2）Study on the performance of Ga₂O₃-based ultraviolet photodetectors with metal semiconductor metal structures.After thermal oxidation growth,Al interdigital electrodes were evaporated on the surface of Ga₂O₃ thin films to prepare a planar MSM structure ultraviolet photodetector.The changes in device performance under different oxidation times were investigated.The device has a dark current below the level of n A at a bias voltage of-5 V and has a significant light response signal under illumination.The calculated response at 255 nm is 8.2 m A/W.However,its response speed is relatively slow.To improve its response speed,we subsequently prepared Ga₂O₃/Ga N heterojunction devices.（3）Preparation and performance study of Ga₂O₃/Ga N heterojunction devices.A layer of Ga₂O₃ thin film is grown on the Ga N thin film by thermal oxidation,and then the top layer of Ga₂O₃ is removed using a wet etching process.Ga₂O₃/Ga N heterojunction devices were fabricated by evaporating appropriate electrodes onto Ga₂O₃ and Ga N thin films,respectively.The effects of growth atmosphere and film thickness on the device were discussed.The optimized device has a light-to-dark ratio of 10⁶ at a bias voltage of-5 V and has a self-powered effect.The response speed of the device has reached 0.6 ms,far exceeding that of the MSM planar device,with a response of 14.3 m A/W under 254 nm light.（4）The optimized device was subjected to plasma RF processing to study the impact of RF on the photoelectric performance of the device.Due to the growth mode of Ga₂O₃,there are a large number of oxygen vacancies and defects during the growth process.Plasma RF processing is used to fill vacancies,further improving the effective carrier count,response speed,and light-to-dark ratio.The light-to-dark ratio increases by about 30 times at a bias voltage of-5 V.