Physical Insights Into Nano-Second Time Scale Cyclic Stress Induced Dynamic R_on Behavior in AlGaN/GaN HEMTs-Part I

In this work, we discuss the physical mechanisms governing the dynamic ON-resistance (ARON) evolution in AlGaN/GaN HEMTs in response to cyclic nanosecond high-field (OFF-state) and hot-electron (semi ON state) stress pulses. The Delta R-ON was found to exhibit a dependence on the number of stress pulses (N), with Delta R-ON initially increasing, followed by a reduction in the rate of increase as N is increased. Experiments were carried out to probe into drain bias, channel current, and stress pulsewidth (PW) dependence of Delta R-ON. A physical mechanism based on pulse-to-pulse modulation of driving forces of trapping, governed by surface and buffer trap charging accumulated over preceding stress pulses, is proposed to explain the observations. Well-calibrated computations are then used to gain further physical insights and to justify the proposed mechanism. Finally, the proposed mechanism is experimentally validated by modulating the trapping/ de-trapping rates and studying their influence on the Delta R-ON evolution.