Electric-field dependent spin diffusion and spin injection into semiconductors

Abstract

We derive a drift-diffusion equation for spin polarization in semiconductors by consistently taking into account electric-field effects and nondegenerate electron statistics. We identify a high electric-field diffusive regime which has no analog in metals. In this regime there are two distinct spin-diffusion lengths. Furthermore, spin injection from a ferromagnetic metal into a semiconductor is enhanced by several orders of magnitude. This enhancement also occurs for high electric-field spin injection through a spin-selective interfacial barrier.