Hot-Phonon Effects on High-Field Transport in GaN and AlN

We have studied the effects of hot phonons on the high-field transport in GaN and AlN. The dynamics of the nonequilibrium electron-longitudinal optical phonon system is studied through an ensemble Monte Carlo code. We find that under steady-state conditions, the hot phonons cause the randomization of the electron momentum, and increase their mean energy leading to diffusive heating. Average electron energies of three and two times those in the equilibrium phonon cases are found for GaN and AlN at the applied fields of 100 and 350 kV/cm, respectively. The electron velocity is reduced compared with the case with equilibrium phonons at the lattice temperature. In the transient regime, peak velocities reached at overshoot are reduced when the nonequilibrium phonons are considered.