Reduced gate leakage and high thermal stability of AlGaN/GaN MIS-HEMTs using ZrO2/Al2O3 gate dielectric stack

In this paper, we report on AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated using ZrO2/Al2O3 as a gate dielectric stack. Gate leakage characteristics as well as dynamic on-resistance due to current collapse have been studied for a ZrO2 (2 nm)/Al2O3 (2 nm)/AlGaN/GaN MIS-HEMT and compared with those for MIS-HEMTs with a single gate insulator of Al2O3 (4 nm) and ZrO2 (4 nm). It was found that an Al2O3 gate insulator was effective in reducing the forward gate leakage and in suppressing the current collapse, whereas the use of the ZrO2 dielectric resulted in a suppressed reverse gate leakage current. The composite ZrO2/Al2O3 MIS-HEMT exhibited superior thermal stability in both gate leakage and dynamic on-resistance up to 200 °C.