High performance normally-off recessed-gate GaN-based MIS-HEMTs achieved by oxygen plasma treatment

We report on the high performance normally-off recessed-gate GaN-based MIS-HEMTs exhibiting excellent combination of maximum drain current (>600 mA/mm) and high positive threshold voltage (+1.3 V) achieved by oxygen plasma treatment. Using the positive threshold voltage shift phenomena previously demonstrated in oxygen plasma treated planar MIS-HEMTs, we were able to achieve robust enhancement-mode operation employing a relatively thick 9-nm-AlGaN barrier layer in the channel region. The rather thick AlGaN barrier may have suppressed remote scattering from insulator/AlGaN interface states leading, to high maximum drain current.