Electrical properties of GaN-based MIS-HEMTs with Al2O3 gate insulator deposited by ALD and mist-CVD techniques

In this work, we compare the performance of AlGaN/GaN metal-insulator-semiconductor high-electron mobility transistors (MIS-HEMTs) with gate dielectric Al2O3 prepared by either ALD or mist-CVD. While for MIS-HEMTS with ALD-Al2O3 gate insulator, the threshold voltage becomes more negative with increasing thickness of Al2O3 as expected, we found that for MIS-HEMTS with mist-Al2O3 gate insulator, the threshold voltage is anomalously almost independent of Al2O thickness. We believe that these findings have potential exciting applications for achieving normally-off operation in AlGaN/GaN MIS-HEMTs.