Application Of Solar-blind Ultraviolet Communication System Based On ?-Ga₂O₃ Material

Due to the absorption of the ozone layer,ultraviolet light with a wavelength in the range of200-280 nm is almost non-existent on the Earth's surface,and is often referred to as "solar blind zone." Communication systems operating in the area are called solar-blind ultraviolet communications.Compared with wireless communication ? infrared communication ? laser communication,solar-blind ultraviolet communication has the advantages of high accuracy ?good confidentiality? free from environmental interference,etc.,become the focus of military competition.UV communication system is the core component of solar-blind ultraviolet photodetector.?-Ga₂O₃ has a band gap of 4.9eV and a corresponding wavelength of 253 nm,and has high thermal stability and chemical stability,and is an ideal blind photodetector material.Due to the defects such as oxygen vacancies in the growth process of ?-Ga₂O₃ thin films,the photodetectors based on pure ?-Ga₂O₃ thin films tend to have high dark current,and the detector performance is not good.In this paper,the growth of Mg-doped ?-Ga₂O₃ thin films is studied,which effectively reduces the oxygen vacancies,reduces the dark current,and improves the performance of detectors.The design of Mg: ?-Ga₂O₃ thin films is also studied.The main results are as follows:?1?Mg-doped ?-Ga₂O₃ thin films were grown on sapphire substrates by magnetron sputtering.Mg-doped ?-Ga₂O₃ thin films were grown on a sapphire substrate at room temperature and atmospheric pressure of 0.8 Pa for 4 hours and then annealed at 800? for 4hours.The results of scanning electron microscopy?SEM?show that the film surface is smooth and the film growth is good.The results of UV absorption test show that Mg-doped ?-Ga₂O₃ thin films have strong absorption to ultraviolet light of less than 200 nm,and the bandgap is over4.9eV,which is sensitive to 254 nm ultraviolet light.The experimental results show that the Mg-doped ?-Ga₂O₃ thin film has a light-to-dark ratio of more than 40 times and a fast response time with a rising time constant10.33rt?28?s and28.84rt?28?s a falling time constant 0.02dt?28?s,has a greater light-dark ratio and faster response time than ?-Ga₂O₃ thin film.?2?Differential pulse modulation and demodulation procedures is developed.Matlab was used to simulate the power,bandwidth and transmission capacity of the common modulationmethod,and choose the differential pulse position modulation?DPPM?modulation method suitable for the system.The DPPM modem program is developed with Verilog HDL,which has the advantages of high reliability,fast communication speed and large transmission capacity.The program designed a number of communication rates,can be tested at different communication rate of the detector performance.?3?The UV wireless communication system based on the field-programmable gate array?FPGA?was designed and built.A switching type UV LED driving circuit was designed using field effect transistor?FET?,and can quickly control the constant current drive LED circuit off.The signal processing circuit is designed and the signal of the detector is amplified and compared with the threshold voltage to reduce the influence of the noise signal.A solar-blind ultraviolet communication system based on ?-Ga₂O₃ thin films was successfully fabricated,the system can test the performance of the detector and provides a good platform for the practical application of detectors.