High RF Performance Enhancement-Mode Al2O3/AlGaN/GaN MIS-HEMTs Fabricated With High-Temperature Gate-Recess Technique

In this letter, we report high-performance enhancement-mode (E-mode) Al₂O₃/AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated with high-temperature low-damage gate recess technique. The high-temperature gate recess is implemented by increasing the substrate temperature to 180 °C to enhance the desorption of chlorine-based etching residues during the dry etching of AlGaN barrier. High-crystal-quality Al₂O₃ gate dielectric was grown by atomic-layer deposition using O₃ as the oxygen source to suppress hydrogen-induced weak bonds. The fabricated E-mode MIS-HEMTs exhibit a threshold voltage of 1.6 V, a pulsed drive current of 1.13 A/mm, and very low OFF-state standby power of $6.8 times 10-8 W/mm at V_GS = 0 V and V_DS = 30 V. At 4 GHz and in pulse-mode operation, the output power density and power-added efficiency were measured to be 5.76 W/mm and 57%, both of which are the highest for GaN-based E-mode MIS-HEMTs reported to date.