Study On The Application Of Surface Plasmons In ?-Ga₂O₃ Based Solar-blind Ultraviolet Photodetector

In recent years,the solar-blind UV photodetector has become a hot research field in the world,mainly due to its wide use in military and civilian applications,such as missile strike warning,fire prevention,and ozone vulnerability monitoring.The development of high-performance solar-blind UV detectors is inseparable from the development of wide bandgap semiconductor materials,including AlGaN,ZnMgO,diamond,and?-Ga₂O₃,in which the direct band gap of?-Ga₂O₃ semiconductor materials is approximately 4.9 eV.?-Ga₂O₃ has a good response to solar-blind UV light and has high transmittance in the mid-ultraviolet,near ultraviolet and visible light range.Besides,it has a good thermal stability and chemical stability.At present,many high-performance?-Ga₂O₃ based solar-blind UV photodetectors have been induced,but still can't fully meet the detection requirements.Therefore,the present work tried to use the localized surface plasmon resonance?SPR?occurs by metal nanoparticles,which enhances the electric field near the metal nanoparticles,and also increases the absorption of solar-blind UV radiation.The effect of plasmons further increased the performance of?-Ga₂O₃ based solar-blind ultraviolet photodetectors.?-Ga₂O₃ films are mainly grown on the sapphire substrate by molecular beam epitaxy.The photodetectors adopt the interdigitated metal-semiconductor-metal structure.In order to generate the surface plasmon resonance in the blind ultraviolet region,aluminum and indium metal were selected as the excitation materials for surface plasmon resonance.The method for preparing metal nanoparticles mainly adopts the nano-sphere lithography technique.By changing the diameter of the polystyrene nano-spheres,metal nanoparticles with different sizes,spacing,and distribution densities were obtained,and their influence on the performance of the photodetector was studied.Meanwhile,aluminum nanoparticles were prepared by rapid thermal annealing method.The effects of aluminum nanoparticles on the surface of?-Ga₂O₃ films were compared with the?-Ga₂O₃ based detectors without aluminum nanoparticles.According to the choice of metals,the content of the paper is divided into two parts,namely the application of surface plasmon on aluminum and the application of surface plasmon on indium.In the research of aluminum surface plasmon,the aluminum nanoparticles formed by rapid ripening annealing have smaller sizes,distributed more densely,and arranged randomly.It effectively reduces the dark current of the detector,and improves the responsivity and detection by 1.5 times and 2 times respectively.Through nano-sphere lithography technology,aluminum nanoparticles have more uniform size and regular arrangement.With the decrease of size and spacing of aluminum nanoparticles,the responsivity and detection have been significantly improved.In the research of indium surface plasmon,the nano-sphere lithography technology is used to prepare indium nanoparticles.The effect is similar to that based on aluminum surface plasmon.The indium nanoparticles with the diameter of 100 nm have greatly improved the photocurrent of the photodetector,while those with the diameter of 200 nm have deteriorated the device performance.In addition,three groups of samples all deteriorated the transient response characteristics.The reason may be related to the presence increased defects at the interface between?-Ga₂O₃ thin film and metal nanoparticles.