Fully recessed-gate normally-off AlGaN/GaN high electron mobility transistors with high breakdown electric field^*

In this letter, the fully recessed-gate normally-off AlGaN/GaN high electron mobility transistors (HEMTs) with N 2 O plasma treatment is fabricated. The roughness and etching depth are measured by Atomic Force Microscope (AFM). The etching depth is about 26 nm and a very low etching rate of 0.29 nm/min is obtained to achieve the accurate etching. In the terms of devices' characteristics, the threshold voltage of recessed-gate HEMT is +1.5 V, and the channel current of recessed-gate HEMTs at VGS-VTH = 1.5 V is about 110 mA/mm. Moreover, 14 mV/V of Drain Induced Barrier Lowering (DIBL) and 70 mV/decade of Subthreshold swing (SS) are achieved in fully recessed-gate normally-off HEMTs. Otherwise, the Schottky reverse leakage current of recessed-gate HEMT is lower than the conventional HEMT by an order of magnitude. More importantly, fully recessed-gate HEMT show the average breakdown electric field at VG=0 V of about 0.85 MV/cm, which is very high value in the fully normally-off recessed-gate HEMTs without metal insulator semiconductor (MIS) structure.