Inhomogeneously-doped semiconductor junctions as a source of~ spontaneous spin polarization

The dynamics of electric-field-driven packets of spin polarized~ carriers passing through an n+/n semiconductor junction have been~ studied. We find that spin packets that are initially very weakly~ spin polarized can have their polarization significantly amplified~ within the junction. The nonlinear spin transport and amplification~ is due to a spin-polarization dependent mobility originating from the Pauli exclusion principle that also~ gives rise to the spin Gunn effect. The spin polarization~ amplification we describe here is driven by the inhomogeneous doping~ density, and thus does not require the large applied electric field~ of the spin Gunn effect. Hence it may apply to situations at low~ electric fields and low temperatures in which spontaneous spin~ polarization has been seen experimentally. We further believe that~ these studies provide a direct way to study the spin-polarization~ dependent mobility in semiconductors.