Role of trapping/detrapping in HTRB Stress and pulsed DC conditions in AlGaN/GaN HEMTs analyzed via TCAD simulations

The reliability issues of AlGaN/GaN high electron mobility transistors (HEMTs) are investigated through technology computer-aided design (TCAD) simulations in order to predict, for the first time, on-wafer stress measurements monitored in the step-stress high-temperature reverse-bias (HTRB) tests and correlate them to the pulsed DC I-V characteristics under zero bias, cold and hot pinch-off. First, the calibration of the TCAD setup is addressed with special focus on the adopted physical models together with the definition of the different trap concentrations. Second, the pulsed DC characteristics are simulated to assess the relevant parameter sensitivities and validate the TCAD approach against experiments at different stress conditions. Third, the HTRB stress is studied in order to evaluate the main features affecting the device when subjected to high voltage and high temperature operations. Results indicated that the main parameters involved in current collapse are donor traps at the passivation/cap interface and the Fe-related acceptor traps given by the doping diffusion in the channel region. The latter affects the pulsed performance, while totally recover in the HTRB regime. Vice versa the partial discharge of the donor traps at the interface plays a key role in the HTRB degradation.