Study On Reliability Of Electrical Stress And Radiation Stress Of Conventional AlGaN/GaN HEMT Devices

GaN-based semiconductor materials have good electrical properties such as large band gap,high electron saturation speed,and large breakdown voltage.They have great potential for development in microwave high-power and high-voltage switching circuits.Reliability issues have always constrained the development of AlGaN/GaN HEMT devices.In some special working environments,the stability of HEMT devices is related to the safety of the entire circuit system.In this paper,the reliability of electrical stress and irradiation stress is studied from both simulated and experimental aspects for conventional depletion-type AIGaN/GaN HEMT devices.The main work of this paper is summarized as follows:1.The Silvaco simulation software was used to simulate the DC characteristics of conventional AlGaN/GaN HEMT devices under open-state stress,and the defects induced by the hot carrier effect in the device when the host is doped to simulate the on-state stress.The hot carriers generated in the device under the on-state stress will escape and be trapped by the trap,causing degradation of the output current and threshold voltage drift of the device.The effects of different location defect states on device performance were investigated using devices of the same structure.It is found that defects in the barrier layer and the surface and the buffer layer degrade the DC characteristics of the device,and the defects in the buffer layer have the greatest influence on the degradation of the device.In addition,the higher the defect concentration,the larger the energy level,and the more significant the degradation.2.The degradation mechanism of the on-state constant-voltage stress and the open-state step stress of AlGaN/GaN HEMT devices was studied,and the reliability of the device under the on-state stress was analyzed.Under the on-state stress,the hot electrons can be injected into the barrier layer and the buffer layer to overcome the barrier height,trapped by traps or generate new traps,resulting in degradation of output current and transconductance,threshold voltage drift and the like.The greater the stress bias,the greater the amount of hot electrons produced,and the greater the energy,the more severe the degradation of the device.According to the reliability problem of electrical stress studied,several electrical stress reinforcement measures are proposed,such as improving the growth process,adopting the passivation structure and field plate structure,and optimizing the buffer layer.3.The degradation mechanism of proton irradiation stress in AlGaN/GaN HEMT devices was investigated,and the reliability of the device under irradiation stress was analyzed.Comparing the DC characteristics of the device before and after the test,it was found that the output current of the device decreased after the proton irradiation,and the threshold voltage drifted positively.Proton irradiation induces an acceptor-type defect inside the device,and the larger the irradiation fluence,the greater the amount of degradation.According to the reliability problem of irradiation stress,the measures to improve the reliability of irradiation stress are proposed from the aspects of growth process,passivation layer material,polarization engineering and device structure.