Development of Enhancement Mode AIN/Ultrathin AlGaN/GaN HEMTs by Selective Wet Etching

摘要

A novel recessed-gate structure involving an ultrathin AlGaN barrier layer capped by an A1N layer in the source-drain access regions has been implemented to demonstrate enhancement-mode high electron mobility transistors. A wet etch process has been developed using heated photoresist developer to selectively etch the A1N for the gate recess step, bypassing plasma etching and associated issues. The etch has been proven to be selective to A1N over AlGaN and GaN. A repeatable threshold voltage of+0.2 IV has been demonstrated with 4 nm AlGaN barrier layer thickness.