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 ( $\Delta {R}_{ \mathrm{\scriptscriptstyle ON}}$ ) evolution in AlGaN/GaN HEMTs in response to cyclic nanosecond high-field (OFF-state) and hot-electron (semi-ON state) stress pulses. The $\Delta {R}_{ \mathrm{\scriptscriptstyle ON}}$ was found to exhibit a dependence on the number of stress pulses ( ${N}$ ), with $\Delta {R}_{ \mathrm{\scriptscriptstyle ON}}$ 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 $\Delta {R}_{ \mathrm{\scriptscriptstyle ON}}$ . 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 $\Delta {R}_{ \mathrm{\scriptscriptstyle ON}}$ evolution.