AVS 49th International Symposium
    Magnetic Interfaces and Nanostructures Monday Sessions
       Session MI+EL-MoM

Paper MI+EL-MoM9
Electrical Spin Injection from NiMnSb into GaAs

Monday, November 4, 2002, 11:00 am, Room C-205

Session: Spintronic Materials and Hybrid Devices
Presenter: W. Van Roy, Imec, Belgium
Authors: W. Van Roy, Imec, Belgium
P. Van Dorpe, Imec, Belgium
V.F. Motsnyi, Imec, Belgium
G. Borghs, Imec, Belgium
J. De Boeck, Imec, Belgium
Correspondent: Click to Email
We demonstrate electrical spin injection from NiMnSb into a GaAs light-emitting diode (LED). We compare single crystalline films grown epitaxially on GaAs(111)B with and without an additional AlAs tunnel barrier, and polycrystalline films grown on top of an AlO@sub x@ tunnel barrier on GaAs(001). The LEDs and NiMnSb films were grown by MBE in two chambers connected under vacuum. For the deposition of AlO@sub x@ tunnel barriers the samples were transported through air to a sputter system for the deposition of Al and oxidation in a controlled O@sub 2@ atmosphere. Spin injection was measured optically at T = 80 K. Electrons were injected with an in-plane spin-component. We used the oblique Hanle effect to transform this spin ensemble into an out-of-plane ensemble and used the circular polarization of the light emitted in the surface-normal direction as a measure of the electrical spin injection. The results were corrected for the out-of-plane tilting of the NiMnSb magnetization in the small oblique magnetic field, and for the MCD effect. We find electrical spin injection of up to 5% for polycrystalline NiMnSb films on top of an AlO@sub x@ barrier. The spin injection drops with increasing bias voltage. The low values indicate a strongly reduced spin polarization for the polycrystalline NiMnSb films. Epitaxial NiMnSb films, especially on (111)B interfaces, are expected to show a much larger spin polarization for the conduction carriers. However, we did not yet observe spin injection from these films. This is attributed to the low interface resistance of this configuration in combination with a NiMnSb surface polarization that, although larger than for the polycrystalline films, is still short of 100%.