Spin transport in antimony-doped germanium detected using vertical spin-valve structures

Abstract

Using a vertical spin-valve structure, we observe spin-dependent transport through antimony (Sb)-doped n-type germanium (n-Ge). Epitaxial intermediate Sb-doped Ge layers can be formed between ferromagnetic CoFe and Fe3Si epilayers on Si(111), where the doping concentration of Sb is estimated to be ∼3 × 1019 cm−3. From the measurement of the current perpendicular to the plane magnetoresistance, we can evidently detect the spin-valve signals from low temperatures up to room temperature. The room-temperature spin diffusion length in the Sb-doped Ge layer can roughly be estimated to be 150–290 nm. By comparing this result and the previous ones, we can clarify the influence of the dopant species on the spin transport even at room temperature in Ge.