High VTH and Improved Gate Reliability in P-GaN Gate HEMTs With Oxidation Interlayer

In this letter, we apply an oxidation technique for p-GaN to a normally-off p-GaN /AlGaN/GaN HEMT to improve the threshold voltage and gate reliability. Oxygen-plasma and low-temperature Oxygen post-annealing treatment (OPAT) of p-GaN before the deposition of gate metal has introduced a 5 nm oxidation interlayer, resulting in a significant improvement in gate breakdown voltage, from 10.4 V to 20.6 V. Thanks to this interlayer, the threshold voltage of p-GaN gate HEMTs is increased from 1.9 V to 4.6 V, while an almost same on- state resistance and a higher drain breakdown voltage are obtained. Time-dependent gate breakdown measurement shows OPAT-HEMTs have a maximum on- state gate drive voltage of 9.2 V for a 10-year lifetime with a 63 % gate failure rate. In addition, a more stable threshold voltage under gate stress indicates the promising application of this technology in GaN power devices.