Nonequilibrium Phonon Effects on Hot-Electron Transport in Semiconductor Heterojunctions.

We have studied the effect of a nonequilibrium population of optical phonons on two-dimensional hot electron transport in a strong external electric field. Comparing with the case of equilibrium phonons, we found that (1) the weak-field mobility due to optical phonon scattering is larger, (2) the normalized mobility decreases faster with the field; and (3) the electron temperature increases much faster with the field. The optical phonon distribution function is strongly anisotropic in the direction of the electric field. The comparison with experiments is discussed.