O3-sourced atomic layer deposition of high quality Al2O3 gate dielectric for normally-off GaN metal-insulator-semiconductor high-electron-mobility transistors

High quality Al2O3 film grown by atomic layer deposition (ALD), with ozone (O3) as oxygen source, is demonstrated for fabrication of normally-off AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs). Significant suppression of Al-O-H and Al-Al bonds in ALD-Al2O3 has been realized by substituting conventional H2O source with O-3. A high dielectric breakdown E-field of 8.5 MV/cm and good TDDB behavior are achieved in a gate dielectric stack consisting of 13-nm O-3-Al2O3 and 2-nm H2O-Al2O3 interfacial layer on recessed GaN. By using this 15-nm gate dielectric and a high-temperature gate-recess technique, the density of positive bulk/interface charges in normally-off AlGaN/GaN MIS-HEMTs is remarkably suppressed to as low as 0.9 x 10(12) cm(-2), contributing to the realization of normally-off operation with a high threshold voltage of +1.6V and a low specific ON-resistance R-ON,R-sp of 0.49 m Omega cm(2). (C) 2015 AIP Publishing LLC.