Velocity overshoot in zincblende and wurtzite GaN

The ultrafast transient behavior of the electron drift velocity and mean energy in zincblende and wurtzite GaN subjected to electric fields E < 100 kV/cm is studied. The evolution of the transport parameters towards the steady state is shown to occur in less than 0.3 ps in both GaN structures. The velocity transient presents an overshoot effect when E > 20 kV/cm and E > 50 kV/cm in the case of zincblende and wurtzite GaN, respectively, even without taking into account intervalley scattering. For a given electric field, the velocity overshoot is always much stronger in the zincblende phase than in the wurtzite phase. (C) 1999 Elsevier Science Ltd. All rights reserved.