Characterization of enhancement-mode AlGaN/GaN high electron mobility transistor using N₂O plasma oxidation technology

In this study, an enhancement-mode (E-mode) AlGaN/GaN high electron mobility transistor (HEMT) using N₂O plasma oxidation process has been performed. Before the gate metal deposition, the AlGaN barrier layer was treated by 135 W N₂O plasma for 240 s. The surface native oxide of AlGaN was removed and a 4 nm high quality Ga₂O₃/Al ₂O₃ compound insulator was simultaneously formed. The threshold voltage of conventional depletion-mode (D-mode) GaN HEMT was -3.6 V and this value can be shifted to 0.17 after N₂O plasma oxidation treatment beneath the gate metal. This 4 nm Ga₂O₃/Al ₂O₃ compound insulator oxidized by N₂O can suppress the polarization charge density for E-mode operation of gate terminal and the gate leakage was also reduced simultaneously.