Evidence for electrical spin tunnel injection into silicon

Electrical spin injection into silicon was studied in a ferromagnet/insulator/silicon/insulator/ferromagnet structure, where the insulator is Si3N4. Si3N4 barriers conduct by hopping conduction at low voltages, but switch to Fowler-Nordheim tunneling at high voltages. In the Fowler-Nordheim tunneling regime a magnetic field dependence of the output current consistent with spin dependent transport through the silicon is observed; in the hopping conduction regime reduced magnetic field dependence of the output current is observed. This voltage dependence of the magnetic sensitivity strongly supports the existence of spin injection into silicon. After correction for Lorentz magnetoresistance, the magnitude of this signal is 4.1%±0.5% (12%±5%) for p-type (n-type) Si.