Research On Radiation Effects Mechanism Of High-voltage GaN HEMT

With the continuous progress of major space projects such as the Tiangong Project and the Chang’e Project,electronic equipment is gradually developing towards miniaturization and lightweight.GaN power devices have potential advantages in aerospace applications due to its high power density,high switching frequency and high temperature resistance.Due to the complex space environment,the performance of GaN power devices are faced with serious degradation,which puts forward higher requirements for the radiation stability of devices.Therefore,based on the p-GaN gate HEMT device,this thesis focuses on the Total Dose Effect(TID)and Single Event Effect(SEE)of ionizing radiation,and analyzes the degradation law of radiation electrochemical characteristics through experiments and simulation to reveal the mechanism of radiation damage.The main research content of this thesis is as followsThe TID of p-GaN gate HEMT devices under different working conditions was studied to reveal the radiation damage mechanism of the device.Under the off-state operating condition,it is found that the off-state leakage,threshold voltage negative drift and reverse gate current of the device increase after radiation.Under the action of the offstate electric field,the holes generated during radiation are accumulated/trapped in the Al GaN barrier layer and GaN channel,which reduces the electron barrier and makes the device easier to open.In particular,a gate current injection test is presented to verify the existence of holes.Under the on-state operating condition,it is found that the forward gate current of the device increases after radiation,while the off state leakage,threshold voltage and reverse gate current of the device almost remain unchanged.Under the action of on-state electric field,radiation introduces a donor-like trap near the metal /p-GaN interface,enhancing the probability of trap assisted tunneling,resulting in enhanced pGaN hole injection and impaired the Schottky junction reverse current blocking ability.The damaged Schottky junction was verified by the gate capacitance testThe SEE of p-GaN gate HEMT devices was studied,and the mechanism of transient current generation after heavy ion incident was revealed.In this thesis,the Sentaurus TACD tool is used to study the effects of different incident locations of heavy ions,different LET values,different incident track lengths and different incident angles on the transient current of heavy ions in the device.The results show that the hole extraction abilities of gate and source are different when the heavy ions incident at different locations,leading to the most significant back channel effect and the strongest SEE transient current when the heavy ions incident at the drain,and the device is most likely to burn out.Due to the difference of holes generated by heavy ions under different LET values,different incident track lengths and different incident angles,the back channel effect is different.As a result,the larger the LET value is,the longer the incident track is and the larger the incident angle is,the larger the SEE transient current is generated,and the easier it is to burn the device.