Nonlinear electron and spin transport in semiconductor superlattices

Nonlinear charge transport in strongly coupled semiconductor super lattices is described by two-miniband Wigner-Poisson kinetic equations with BGK collision terms. The hyperbolic limit, in which the collision frequencies are of the same order as the Bloch frequencies due to the electric field, is investigated by means of the Chapman-Enskog perturbation technique, leading to nonlinear drift-diffusion equations for the two miniband populations. In the case of a lateral superlattice with spin-orbit interaction, the corresponding drift-diffusion equations are used to calculate spin-polarized currents and electron spin polarization.