Normally-Off Metal-Insulator-Semiconductor P-GaN gated AlGaN/GaN high electron mobility transistors with low gate leakage current

Abstract

In this study, a normally-off AlGaN/GaN metal–insulator-semiconductor high electron mobility transistors (MIS-HEMTs) with p-GaN layer were processed, which possess a high threshold voltage and a low gate leakage current due to metal–insulator-semiconductor (MIS) gate structure. A SiNx layer as the insulator layer was deposited between p-GaN layer and gate electrode. The dependent of device performance on SiNx thickness was investigated. Moreover, the threshold voltage of normally-off MIS-HEMT was emphatically discussed with different insulator layer thickness. It demonstrates that obviously positive shifting for threshold voltage from 1.5 to 6 V was achieved by increasing the SiNx thickness from 0 to 20 nm, while the channel mobility was comparable for all samples. Besides, the introduction of MIS gate structure is also beneficial for suppressing the gate leakage current and improving the maximum gate voltage swing owing to the high breakdown field of approximately 8.3 MV/cm.