Characteristic Of P-GaN Gate Devices Under UIS Stress/Neutron Irradiation

GaN-based power devices have the advantages of high operating frequency,low loss,and high temperature resistance,which can effectively improve the efficiency and power density of power electronic systems,so they have broad application prospects in data centers,motor drives,and aerospace.And P-GaN gate devices have been commercialized due to their enhanced characteristics,performance and cost advantages,but they usually face complex dynamic stress and irradiation environments in their practical applications.Currently,the research on the influence of UIS stress and neutron irradiation on the characteristics of P-GaN devices is not sufficient,and the structure and working principle of GaN-based power devices are different from Si-based power devices,and it is impossible to directly refer to the theory of UIS stress and irradiation of Si-based power devices.To further improve the advantages of P-GaN gate devices in power electronic systems,it is necessary to study the influence of UIS stress and neutron irradiation on the characteristics of P-GaN gate devices.In this work,the impact of UIS stress and neutron irradiation on P-GaN gate GaN HEMTs is investigated.The major works are as following:（1）A test circuit combining UIS circuit and double pulse test（DPT）circuit is designed.It can simulate UIS stress under different conditions faced by P-GaN gate devices in practical applications,and can accurately characterize the dynamic on-resistance of P-GaN gate devices within microseconds and milliseconds after the end of UIS electrical stress,which provides an experimental basis for the study of dynamic on-resistance shift of P-GaN gate devices under UIS stress.（2）The physical mechanism of the dynamic on-resistance shift of P-GaN gate devices under UIS stress is proposed.By measuring the dynamic on-resistance of P-GaN gate devices after UIS stress,it is observed that the dynamic on-resistance decreases abnormally under UIS stress.The measurement results of different UIS stress conditions are further analyzed,and the physical mechanism of the asynchronous emission of electrons and holes related to impact ionization is clarified.Mathematical model of on-resistance evolution over time is built based on the proposed mechanism,which is verified the by Sentaurus simulation and measurement.（3）The physical mechanism of gate degradation of P-GaN gate devices under neutron irradiation is proposed.After neutron irradiation at energy of 1 Me V and a fluence of 6×10¹³ and 1×10¹⁴ n/cm2,the gate stack degenerates with increased threshold voltage and increased gate leakage current.Through C-V test and pulse I-V test,the density and energy level of electron traps and hole traps in the gate stack are obtained,and it is concluded that neutron irradiation produces V_Ga and Ga_i in GaN through displacement damage,and interacts with other defects to form electron traps respectively.And the pure dislocation could be transformed to V_Ga-decoration dislocation,and the energy of V_Ga-decoration dislocation is lower than the energy of pure dislocation under conduction band minimum.