Reliability of Enhancement-mode AlGaN/GaN HEMTs Under ON-State Gate Overdrive

The ON-state reliability of enhancement-mode AlGaN/GaN HEMTs fabricated by fluorine plasma implantation technology under gate overdrive is reported. A critical gate forward voltage (V(GC)) is observed, beyond which the turn-on voltage of the 2DEG channel exhibits a negative shift. This phenomenon is proposed to be caused by the impact ionization of the F ions in the barrier layer by hot electron injection. The proposed physical model is further validated by the temperature-dependent characterization of V(GC) that shows an eventual stabilization at higher temperatures (> 125 degrees C), owing to the efficient removal of hot electrons by phonon scattering. The determination of V(GC) provides valuable guideline for the design of gate drive circuits of GaN power circuits