Highly efficient room-temperature tunnel spin injector using CoFe/MgO(001)

Semiconductor spintronics is a promising technology in which the spin states of electrons are utilized as an additional degree of freedom for device operation. One of its prerequisites is the ability to inject spin-polarized electrons into semiconductors. An overview is presented of recent progress in spin injection using an injector based on a crystalline CoFe/MgO(001) tunnel structure. The spin polarization of the electrons that were injected into a GaAs quantum-well light-emitting diode was inferred from electroluminescence polarization from the quantum well. Spin polarizations of 57% at 100 K and 47% at room temperature were obtained. The spin polarization was found to exhibit a strong dependence on bias and temperature, which can be explained on the basis of spin relaxation within the GaAs.