  We present a novel p-GaN gate HEMT structure with reduced hole concentration
near the Schottky interface by doping engineering in MOCVD, which aims at
lowering the electric field across the gate. By employing an additional
unintentionally doped GaN layer, the gate leakage current is suppressed and the
gate breakdown voltage is boosted from 10.6 to 14.6 V with negligible influence
on the threshold voltage and on-resistance. Time-dependent gate breakdown
measurements reveal that the maximum gate drive voltage increases from 6.2 to
10.6 V for a 10-year lifetime with a 1% gate failure rate. This method
effectively expands the operating voltage margin of the p-GaN gate HEMTs
without any other additional process steps.
