Cross-sectional imaging of spin injection into a semiconductor

Recent discoveries of phenomena that relate electronic transport in solids to the spin angular momentum of the electrons are the fundamentals of spin electronics (spintronics). The first proposed conceptual spintronic device, the spin field-effect transistor which has not yet been successfully implemented-requires the creation and detection of spin-polarized currents in a semiconductor. Whereas electrical spin injection from a ferromagnetic metal into GaAs has been achieved recently, the detection techniques used up to now have drawbacks like the requirement of large magnetic fields or limited information about the spin polarization in the semiconductor. Here we introduce a method that, by observation across a cleaved edge, enables us to directly visualize fully remanent electrical spin injection into bulk GaAs from a ferromagnetic contact, to image the spin-density distribution in the semiconductor in a cross-sectional view and to separate the effects of spin diffusion and electron drift.