  We demonstrate electrical injection and detection of spin-polarized electrons
in silicon (Si) using epitaxially grown Fe_3Si/Si Schottky-tunnel-barrier
contacts. By an insertion of a delta-doped n^+-Si layer (~ 10^19 cm^-3) near
the interface between a ferromagnetic Fe_3Si/Si contact and a Si channel (~
10^15 cm^-3), we achieve a marked enhancement in the tunnel conductance for
reverse-bias characteristics of the Fe_3Si/Si Schottky diodes. Using laterally
fabricated four-probe geometries with the modified Fe_3Si/Si contacts, we
detect nonlocal output signals which originate from the spin accumulation in a
Si channel at low temperatures.
