Reliability of p-GaN Gate HEMTs in Reverse Conduction

Synchronous buck converter comprises a low side (LS) and a high side (HS) switch, where the HS switch works in the first quadrant (forward conduction) whereas the LS switch works in the third quadrant (reverse conduction). However, the reliability of the p-GaN gate high electron mobility transistor (HEMT) in reverse conduction is unclear. In this work, a comprehensive evaluation of this conduction mode for 200-V HEMTs was conducted. First, devices were subjected to time-dependent breakdown (TDB) measurements. By comparing different device configurations, the time to failure (TTF) was found to only scale with the number of gate fingers instead of the gate width
${W}_{G}$
, proving the critical spots are the intersection of gate fingers over the N implantation isolation. The reverse operation voltage of
${V}_{DS}$
for ten years lifetime was extrapolated to be −5.4 V, corresponding to a failure of 0.01% and 100 gate fingers. Second, the devices were submitted to 200-V
${V}_{DS}$
OFF-state stress for 10 s, after which the reverse drain current saw a negligible degradation. Third, the reverse conduction of the HEMTs only showed a very limited deterioration after a long-time bias temperature instability (BTI) stress at
${V}_{DS} = - 5.5$
V and
${V}_{GS} = 0$
V. This work proves the p-GaN gate HEMTs bear a high reliability in reverse conduction, which can simplify the design of synchronous power system.