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 n_s 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.