  We present a study of spin transport in charge and spin inhomogeneous
semiconductor systems. In particular, we investigate the propagation of
spin-polarized electrons through a boundary between two semiconductor regions
with different doping concentrations. We use a theoretical and numerical
method, presented in this paper, based on a self-consistent treatment of a
two-component version of the Boltzmann transport equation. We show that
space-charge effects strongly influence the spin transport properties, in
particular giving rise to pronounced spin accumulation and spin density
enhancement.
