1.8 kV AlGaN/GaN HEMTs with High-k/Oxide/SiN MIS Structure

We report the fabrication of AlGaN/GaN high electron mobility transistors (HEMTs) having metal-insulator-semiconductor (MIS) gate structure with the high-A/SiN and high-k/oxide/SiN insulator structures. The SiO₂ and Al₂O₃ were used as the oxide, and the HfO₂, ZrO₂ and TiO₂ were used as the high-k materials. Both high-k/SiN and high-k/oxide/SiN MIS-gate HEMTs showed good DC operating characteristics. However, there was significant difference in the breakdown voltage characteristics. In the case of the high-k/oxide/SiN MIS-HEMT, the off-state drain current was significantly reduced due to the presence of the SiO₂ or Al₂O₃ layer, and the breakdown voltage characteristics were improved. The breakdown voltage of HfO₂/SiO₂/SiN and ZrO₂/SiO₂/SiN MIS-HEMT for the gate-drain distance L_gd = 28 mum were 1.8 kV and 1.7 kV, respectively.