High-temperature low-damage gate recess technique and ozone-assisted ALD-grown Al2O3 gate dielectric for high-performance normally-off GaN MIS-HEMTs

A high-temperature (180 °C) gate recess technique featuring low damage and in-situ self-clean capability, in combination with O₃-assisted atomic-layer-deposition (ALD) of Al₂O₃ gate dielectric, is developed for fabrication of high performance normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs), which exhibit a threshold voltage of +1.6 V, a pulsed drive current of 1.1 A/mm, and low dynamic ON-resistance under hard-switching operation. Chlorine-based dry-etching residues (e.g. AlCl₃ and GaCl₃) are significantly reduced by increasing the wafer temperature during the gate recess to their characteristic desorption temperature, while defective bonds like Al-O-H and positive fixed charges in ALD-Al₂O₃ are significantly suppressed by substitution of H₂O with O₃ precursor.