Scattering-assisted electric current in semiconductor superlattices in the Wannier-Stark regime

We have used the Monte Carlo technique to investigate the mechanism of scattering-assisted charge transport in semiconductor superlattices under a strong applied electric field in the Wannier-Stark (WS) regime. The distribution function of quasi-two-dimensional carriers localized in each WS level is calculated, and the contributions of different scattering mechanisms to the total scattering probability are analyzed. Based on these results, the drift velocity is derived as a function of the applied electric field. Due to the LO-phonon-induced resonant transfer of electrons between different spatially localized WS states, our calculated I-V characteristics oscillates with clear negative differential velocity behavior. At the electric field strength such that the Bloch oscillation energy is equal to an integer multiple of the LO phonon energy, a peak appears in the I-V curve. Our theoretical result agrees with the experimental data which was obtained from analyzing the terahertz response of superlattices to picosecond optical pulse excitation.