Study On Electrical Characteristics And Optoelectronical Characteristics Of AlGaN/GaN Schottky Barrier Diode

In recent years,GaN-based wide band gap semiconductor devices have gradually become one of the research hotspots in the semiconductor field.This paper uses a GaN-based heterojunction material-AlGaN/GaN to produce a horizontal Schottky barrier diode.At the heterojunction interface,The horizontal 2DEG conductive channel with high concentration and high electron mobility can be formed without doping.It can help us overcome the structural defects caused by the peeling of the vertical GaN bulk material.Because of the material's wide band gap,high breakdown electric field,high saturated electron drift speed and other excellent characteristics,AlGaN/GaN SBDs not only have broad application prospects in high-power power electronic systems,but also have a place in the field of high-performance UV photodetectors.This article uses these application directions as the starting point for research.The 2DEG generation mechanism of AlGaN/GaN heterojunction materials and the working principle of SBD are used as the theoretical basis for research.We explore the effects of various factors on the electrical characteristics and optoelectronical characteristics of the device.The main research results are as follows:In the field of power electronic applications,the electrical characteristics of the device are mainly researched.Low leakage current,low turn-on voltage and high breakdown voltage are the research's goals.Using sapphire as the device's substrate material,a Ni/Au groove anode AlGaN/GaN Schottky diode was prepared as a standard device.The device was optimized from the material and structure of the anode.First,the original Ni/Au anode was replaced with W anode to optimize the electrical characteristics of the device.It can greatly decrease the turn-on voltage from 0.84V to 0.35V.It can also make the device obtain lower reverse leakage current and higher breakdown voltage,but it will increase the on-resistance of the device.This is mainly due to W has lower work function.It can effectively reduce the height of the barrier.At the same time,the electron's coupling between the metal's electrons and the semiconductor's surface state is stronger.The concentration of the positive charge trap on the surface and the 2DEG concentration at the heterojunction interface are reduced.Second,we deposited a thin(0?2nm)Al₂O₃ insulating dielectric layer on the device's anode groove to modify the metal-semiconductor interface.It weakens the electric field strength at the interface,makes the reverse characteristics of the device significantly improved,and makes the device obtain lower reverse leakage current and higher breakdown voltage.Finally,the temperature-variable electrical characteristics of the optimized device are analyzed.In the temperature range of 25??150?,the device has stable electrical characteristics.The turn-on voltage becomes smaller as the temperature increases,and the on-resistance and reverse leakage current increase gradually as the temperature increases.In the application of UV photodetectors,the photoelectrical characteristics of the device are mainly studied.Based on the research of power electronic devices,transparent/translucent electrodes are used to replace the original thick metal electrodes with poor light transmission to prepare high-performance Schotty UV photodetectors.Starting from the substrate,the UV light and the anode's materials and structures,the effects of these on the device's optoelectronical characteristics were experimentally investigated.By replacing the sapphire substrate with a SiC material,the device's response and detection capabilities are improved significantly.This may be due to the fact that the epitaxially grown material on the SiC substrate has a smoother surface and fewer dislocations and defects.In terms of the UV light,other variables are strictly controlled.It is found that the device is more sensitive to the UV light of 365nm and its photoelectrical conversion capability is stronger than the UV light of 254nm.This is mainly due to high frequency light brings greater reflection loss.The greater the light intensity,the greater the electrical signal generated by the device,but the lower the photoelectrical conversion efficiency of the device.In terms of the anode's materials and structures,the translucent metal anode can significantly reduce the dark current of the device.Due to the decrease in light transmittance,it will also cause the device's photoelectrical conversion capacity to decrease significantly.Finally,an Al₂O₃ dielectric layer with different thickness(0?2nm)is inserted in the ITO-semiconductor interface.The conversion capability of the device is slightly reduced.The background noise of the device is optimized by the blocking effect of the insulating layer on the current between the interfaces.It also can significantly improve the detection capability of the device.