Effect of gate dielectrics on characteristics of high-energy proton-irradiated AlGaN/GaN MISHEMTs

The effects of high energy (57 MeV) proton irradiation on the electrical characteristics of AlGaN/GaN MISHEMTs were investigated. The MISHEMTs were fabricated with two different types of gate dielectrics, atomic layer deposited (ALD)-Al2O3 and plasma enhanced chemical vapor deposited (PECVD)-SiNx. It was found that the proton irradiation induces negative charges in gate dielectric layers, which would degrade performances of the MISHEMTs, such as threshold voltage shift and reduction of drain current. After proton irradiation, the increase of the induced charge density in the MISHEMT with Al2O3 gate dielectric layer was not severe, which resulted in less degradation of DC characteristics of the device, but the increase of the induced charge density was seven times higher in the MISHEMT with SiNx gate dielectric layer to cause a larger positive shift of threshold voltage in the transfer characteristic of the device. These results indicated that the Al2O3 dielectric layer is more suitable as the rad-hard gate insulator for AlGaN/GaN MISHEMTs in the space environment.