Hot-electron transient transport in a superlattice miniband

Abstract

The authors analyse hot-electron transient transport in a Bloch-type superlattice miniband, under conditions leading to saturation in the regime of negative differential conductance (NDC), using a balance equation approach with a dynamical force-balance equation for the centre-of-mass acceleration, and a dynamical energy balance. They solve these balance equations numerically for a GaAs-based superlattice, considering Gamma -valley electrons with a tight-binding miniband structure. Both impurity scattering and phonon scattering are taken into account. For a step electric field in the NDC regime, the drift velocity exhibits very pronounced overshoot. In GaAs systems, the maximum drift velocities occur within 0.1-0.3 ps after turning on an electric field of 10 kV cm-1. About this time, the instantaneous inverse effective CM mass for perpendicular transport falls within the range of negative values. The rise of the electron temperature, however, is much slower, such that the behaviour of the drift velocity response to an impulsive electric field is markedly dependent on the duration of the impulse.