Investigation of the effects of spin injection of charge carriers from a ferromagnetic Ni(Co)/GaAs Schottky contact in quantum well heterostructures

The circularly polarized electroluminescence of quantum-confined InGaAs/GaAs heterostructures with a ferromagnetic Ni(Co)/GaAs Schottky contact has been investigated. It is shown that the high degree of circular polarization (to 42%) is due to the injection of spin-polarized holes from the ferromagnetic metal. The dependence of the spin injection efficiency on the type of the metal/GaAs interface and the quantum well depth has been analyzed. The spin coherence length of holes was found to be ≈80 nm at 1.5 K.