We have developed a non-local architecture for spin current injection, manipulation, and detection in n-doped bulk Si at room temperature. Spins are locally generated at the indirect gap of bulk Si by means of circularly polarized light and then detected by exploiting the inverse spin-Hall effect (ISHE) occurring inside a thin Pt pad deposited at the top of the Si substrate. We demonstrate that it is possible to modulate the transport properties of the optically injected spin current by applying a bias voltage along the direction of motion of the particles. In this case, we are able to explore both the spin diffusion regime, characterized by a spin diffusion length Ls ≈ 12 μm, and the spin drift regime with applied electric fields up to E = 35 V/cm. We demonstrate that the spin transport length of the electrons can be increased (or decreased) by more than 100% for electric fields antiparallel (or parallel) to the diffusion direction. As a consequence, the ISHE signal can be electrically controlled to have high or low output voltages from the non-local device.
