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(Vₜₕ)shifts have been revealed: a rapidVₜₕshift at low doses[< 3 krad (SiO₂)]for both HEMTs and MOS-HEMTs, and an additionalVₜₕshift only found in MOS-HEMTs for doses up to at least 2 Mrad( SiO₂). The rapidVₜₕshift anneals quickly and is a strong function of layer material. We attribute this portion of theVₜₕshift to hole trapping in the AlGaN barrier layer. TheVₜₕshift at high doses found only in MOS-HEMTs is attributed to hole trapping in the gate oxide. By comparing MOSFETs withHfO₂andAl₂ O₃gate dielectrics that are annealed during processing at various temperatures, we find that500∘ CannealedHfO₂shows the most promising TID response.