Electrical Spin Injection in a Ferromagnetic Metal/Insulator/Semiconductor Tunnel Heterostructure

We demonstrate experimentally the electrical spin injection from a ferromagnetic metal/tunnel barrier contact into a semiconductor III–V heterostructure. The injected electrons have an in-plane spin orientation. We show that by applying an oblique external magnetic field this spin orientation can be manipulated within the semiconductor, and a nonzero perpendicular spin component arises. This perpendicular component can be easily monitored by optical means (circular polarization of the emitted light). In a CoFe/AlO _x /(Al,Ga)As/GaAs heterostructure we observe injected spin polarization in access of 9% at 80 K and optimized structures have recently shown spin injection up to room temperature.