Reduced gate leakage and high thermal stability of AlGaN/GaN MIS-HEMTs using ZrO_2/Al_2O_3 gate dielectric stack

摘要

In this paper, we report on AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) fabricated using ZrO_2/ Al_2O_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_2O_3 (2 nm)/AlGaN/GaN MIS-HEMT and compared with those for MIS-HEMTs with a single gate insulator of Al_2O_3 (4 nm) and ZrO_2 (4 nm). It was found that an Al_2O_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_2O_3 MIS-HEMT exhibited superior thermal stability in both gate leakage and dynamic on-resistance up to 200℃.