Electrical characterization of AlGaN/GaN HEMTs fabricated on CF4-plasma-treated AlGaN surface

In this work, we have studied the mechanism of the threshold voltage shift for AlGaN/GaN HEMTs by exposing the AlGaN surface to CF4 plasma. The CF4 plasma treatment on AlGaN/GaN heterostructures resulted in the decrease in two-dimensional electron gas density. Careful observation on the AlGaN surface indicated that the AlGaN surface was slightly etched after CF4 plasma exposure. The rate of ns decrease was much larger than that calculated by assuming surface AlGaN etching, indicating that the threshold voltage of the AlGaN/GaN heterostructure was also shifted by the effects of F ion implantation into the AlGaN surface layer.