Low Leakage Current and High Breakdown Field AlGaN/GaN MIS-HEMTs Using PECVD-SiNx as a Gate Dielectric

In this paper, SiNx film deposited by plasma-enhanced chemical vapor deposition was employed as a gate dielectric of AlGaN/GaN high electron mobility transistors (HEMTs). We found that the NH(3) flow during the deposition of SiNx can significantly affect the performances of metal–insulator–semiconductor (MIS) HEMTs. Compared to that without using NH(3) flow, the device with the optimized NH(3) flow exhibited three orders of magnitude lower gate leakage current, two orders of magnitude higher ON/OF drain current ratio, and an increased breakdown field by 69%. In addition, an in situ N(2) plasma surface treatment prepared prior to SiNx deposition can further improve DC performances of MIS-HEMTs to a very low gate leakage current of 10(−9) mA/mm and a high ON/OFF drain current ratio up to 10(9) by reducing the interface state density. These results demonstrate the great potential for using PECVD-SiNx as a gate dielectric in GaN-based MIS-HEMTs.