Bandstructure effect on high-field transport in GaN and GaAlN

The velocity-held characteristics in zinc-blende GaN are calculated from the Boltzmann equation, using realistic energy bands taken from ab initio theory. The drift velocity and the high-field negative differential resistance are shown to be largely determined by the inflection point in the bands centered around the Gamma valley, instead of the usual intervalley scattering. We analyze the relative importance of these competing mechanisms for GaN and Al0.5Ga0.5N. The importance of this anomaly to device properties is also discussed. (C) 1997 American Institute of Physics.