Alleviation of the on-state dynamic conductance decline in a GaN high electron mobility transistor with heavy carbon doping

Carbon doping is a standard blocking-voltage-enhancing technique for commercial silicon substrate-based AlGaN/GaN power switching transistors, although the incorporation of carbon into GaN may deteriorate the dynamic on-state resistance (dy- R on ) properties of the device. Commonly, researchers have believed that the greater the carbon doping, the greater the deterioration in dy- R on . Surprisingly, in this work, the opposite was observed: the dy- R on value decreased as the carbon concentration increased, particularly when the density exceeded several 10 17 cm −3 . This phenomenon is explained by the effect of electric field-induced band-to-band electron tunneling into the two-dimensional electron gas (2DEG) conduction channel, originating from the ionization of acceptor-like nitrogen site carbon atoms (C N ) in the device off-state with large drain bias. Simulation data indicated that negatively ionized C N may generate a much larger electric field in samples with higher carbon doping, which may induce a narrower 2DEG back energy band barrier that increases the possibility of electron band-to-band tunneling.