Normally-off AlGaN/GaN high-electron-mobility transistor on Si(111) by recessed gate and fluorine plasma treatment

We have studied the efficiency of using both recessed gate and fluorine plasma treatment to achieve normally-off high-electron-mobility transistor (HEMT). It is found that, by a simple recess process, one cannot achieve normally off device with high drain current because of gate leakage problem after inductively coupled plasma (ICP) etching for recessed structure. The proper method is adding fluorine treatment based on recess gate. The normally off GaN HEMTs with recess gate and fluorine treatment show very good performance. It is found that the threshold voltages can be shifted to +1.1V, and the drain current at V-GS - V-th = 2V and V-DS = 20V was 218 mA/mm. (C) 2016 The Japan Society of Applied Physics