Reliability of p-GaN Gate HEMTs in Reverse Conduction

Abstract

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> , proving the critical spots are the intersection of gate fingers over the N implantation isolation. The reverse operation voltage of V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> 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 VDS 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> = -5.5 V and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> = 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.