Reduced gate leakage and high thermal stability of AlGaN/GaN MIS-HEMTs using ZrO2/Al2O3gate dielectric stack

In this paper, we report on AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated using ZrO 2 /Al 2 O 3 as a gate dielectric stack. Gate leakage characteristics as well as dynamic on-resistance due to current collapse have been studied for a ZrO 2 (2 nm)/Al 2 O 3 (2 nm)/AlGaN/GaN MIS-HEMT and compared with those for MIS-HEMTs with a single gate insulator of Al 2 O 3 (4 nm) and ZrO 2 (4 nm). It was found that an Al 2 O 3 gate insulator was effective in reducing the forward gate leakage and in suppressing the current collapse, whereas the use of the ZrO 2 dielectric resulted in a suppressed reverse gate leakage current. The composite ZrO 2 /Al 2 O 3 MIS-HEMT exhibited superior thermal stability in both gate leakage and dynamic on-resistance up to 200 °C.