Abstract
In this letter, we propose using an oxide-filled isolation structure followed by N 2 H 2 postgate annealing to reduce the leakage current in AlGaN/GaN HEMTs. An off-state drain leakage current that is smaller than 10 -9 A/mm (minimum 5.1× 10 -10 A/mm) can be achieved, and a gate leakage current in the range of 7.8 × 10 -10 to 9.2 × 10 -11 A/mm (V GS from-10 to 0 V and VDS = 10 is obtained. The substantially reduced leakage current results in an excellent on/off current ratio that is up to 1.5 × 10 8 . An improved flicker noise characteristic is also observed in the oxide-filled devices compared with that in the traditional mesa-isolated GaN HEMTs. © 2006 IEEE.