Separation of hot-electron and self-heating effects in two-dimensional AlGaN/GaN-based conducting channels

We address experimental and theoretical study of a two-dimensional electron gas transport at low and moderate electric fields. The devices under study are group-III nitride-based (AlGaN/GaN) gateless heterostructures grown on sapphire. The transmission line model patterns of different channel lengths, L, and of the same channel width are used. A strong dependence of the device I-V characteristics on the channel length has been found. We have developed a simple theoretical model to adequately describe the observed peculiarities in the I-V characteristics measured in steady-state and pulsed (10(-6) s) regimes. The effect of the Joule heating of a heterostructure is clearly distinguished. The thermal impedance and the channel temperature rise caused by the Joule self-heating have been extracted for the devices of different L at different values of dissipated power. The current reduction due to both self-heating and hot-electron effects is determined quantitatively as a function of the electric field. (C) 2003 American Institute of Physics.