Total-Ionizing-Dose Radiation Effects in AlGaN/GaN HEMTs and MOS-HEMTs

We have investigated the total ionizing dose (TID) radiation effects in AlGaN/GaN MOS-HEMTs as a function of dose and radiation bias, and compared them with conventional HEMTs. Under 10 keV X-ray irradiation, two distinct regimes of threshold voltage (V-th) shifts have been revealed: a rapid V-th shift at low doses [< 3krad(SiO2)] for both HEMTs and MOS-HEMTs, and an additional V-th shift only found in MOS-HEMTs for doses up to at least 2 Mrad (SiO2). The rapid V-th shift anneals quickly and is a strong function of layer material. We attribute this portion of the V-th shift to hole trapping in the AlGaN barrier layer. The V-th shift at high doses found only in MOS-HEMTs is attributed to hole trapping in the gate oxide. By comparing MOSFETs with HfO2 and Al2O3 gate dielectrics that are annealed during processing at various temperatures, we find that 500 degrees C annealed HfO2 shows the most promising TID response.