High-Voltage-Stress Induced Degradation and Radiation Response of GaN-Based HEMTs
GaN-based HEMTs are increasingly popular for use in space-based, high-power, high-voltage and high temperature applications due to the large band gap, high breakdown electric field, low carrier generation rate by thermal activation, and high mobility two-dimensional electron gas (2DEG) at the heterointerface. In this work, high-voltage-stress induced degradation and radiation response of GaN-based HEMTs are studied. Low-frequency noise measurements are performed to characterize the defects before and after stress/irradiation. First, the effects of hot-carrier stress at temperatures up to 125 oC are evaluated for industrial-quality AlGaN/GaN HEMTs biased in the ON, semi-ON, and OFF states. Both donor-like and acceptor-like defects can play significant roles in the device degradation, with densities depending on stress time, temperature, and bias condition. The worst-case transconductance degradation is observed under ON bias condition at elevated temperatures. Dehydrogenation of ON-H impurity complexes during ON-bias stress and the resulting increases in densities of ON-related donor-like defects are evidently the reliability-limiting mechanism in these devices. Then we evaluate the effects of 10-keV X-ray irradiation, 1.8 MeV proton irradiation, and high-voltage stress on three kinds of GaN HEMTs: two kinds of industrial-grade AlGaN/GaN HEMTs and one research-grade InAlN/GaN HEMT. ON-related donors, VN-related acceptors and NGa-related acceptors are the main defects dominating the radiation response and reliability of these devices.