AlGaN/GaN HEMTs With Low Leakage Current and High On/Off Current Ratio

In this letter, we propose using an oxide-filled isolation structure followed by N₂/H₂ 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^-11A/mm (V _GS from -10 to 0 V and V _DS = 10 V) is obtained. The substantially reduced leakage current results in an excellent on/off current ratio that is up to 1.5 ?? 10⁸. An improved flicker noise characteristic is also observed in the oxide-filled devices compared with that in the traditional mesa-isolated GaN HEMTs.