Proton irradiation-induced traps causing VT instabilities and RF degradation in GaN HEMTs

Using quantitative high-electron-mobility-transistors (HEMTs)-based defect spectroscopy, the degradation mechanisms of GaN HEMTs subjected to proton irradiation were explored to understand how these devices would operate in high radiation applications. It was observed that proton irradiation in GaN HEMTs caused a permanent threshold voltage (V_T) shift (0.59 V) that led to a 30% reduction in I_{DS, max} due to deep traps formed near the valence band edge, and V_T dispersion (i.e., time-and voltage-dependent V_T instability) increased by ~0.10 V as a result of an E_C-0.72 eV trap that is most likely located in the GaN buffer layer. While RF accelerated life testing with no irradiation exposure in previous work resulted primarily in E_C-0.57 eV GaN buffer defect formation/activation localized in the drain access region, the proton irradiation in this work causes degradation through V_T shifts mostly through trapping effects under the gate. These results indicate that degradation mechanisms depend strongly on the stressors, and that different defects can cause multiple pathways for HEMT degradation.