Gao F, Chen D, Tuller H L, et al. On the redox origin of surface trapping in AlGaN/GaN high electron mobility transistors[J]. Journal of Applied Physics, 2014, 115(12): 124506.

ABSTRACT

Water-related redox couples in ambient air are identified as an important source of the surfacetrapping states, dynamic on-resistance, and drain current collapse in AlGaN/GaN high electronmobility transistors (HEMTs). Throughin-situX-ray photoelectron spectroscopy (XPS), directsignature of the water-related species—hydroxyl groups (OH) was found at the AlGaN surface atroom temperature. It was also found that these species, as well as the current collapse, can bethermally removed above 200C in vacuum conditions. An electron trapping mechanism based onthe H2O/H2and H2O/O2redox couples is proposed to explain the 0.5 eV energy level commonlyattributed to the surface trapping states. Finally, the role of silicon nitride passivation in successfullyremoving current collapse in these devices is explained by blocking the water molecules away fromthe AlGaN surface.