Imaging spin diffusion in germanium at room temperature

Abstract : We report on the nonlocal detection of optically oriented spins in lightly n-doped germanium at room temperature. Localized spin generation is achieved by scanning a circularly polarized laser beam (λ = 1550 nm) on an array of lithographically defined Pt microstructures. The in-plane oriented spin generated at the edges of such microstructures, placed at different distances from a spin-detection element, allows for a direct imaging of spin diffusion in the semiconductor, leading to a measured spin diffusion length of about 10 μm. Two different spin-detection blocks are employed, consisting of either a magnetic tunnel junction or a platinum stripe where the spin current is converted in an electrical signal by the inverse spin-Hall effect. The second solution represents the realization of a nonlocal spin-injection/detection scheme that is completely free from ferromagnetic functional blocks.