90 nm gate length enhancement-mode AlGaN/GaN HEMTs with plasma oxidation technology for high-frequency application

High-frequency enhancement-mode (E-mode) AlGaN/GaN high-electron-mobility transistors (HEMTs) with plasma oxidation technology (POT) were fabricated through plasma-enhanced chemical vapor deposition. POT enables the formation of a thin oxide layer in the gate region, which decreases the gate leakage by at least two orders of magnitude compared with conventional recessed gate HEMTs. Ultra-low leakage was achieved in the fabricated device, with I_off = 9.5 × 10⁻⁷mA/mm and a high ON/OFF ratio of over 10⁹. Good suppression of current collapse was obtained after the application of POT in the access region. The enhancement-mode AlGaN/GaN HEMTs with POT showed an outstanding performance, with a V_th of 0.4 V, a maximum drain current of 965 mA/mm, and an f_max of 272 GHz.