Spin - Polarized electronics using dilute magnetic semiconductors

The realization of spin polarized current injection into a semiconductor using metallic ferromagnetic contacts has so far remained elusive. We present here, a simple diffusive transport model that explains the negative results of previous experiments as resulting from a conductivity mismatch between the ferromagnetic contacts and the semiconductor. Moreover, we demonstrate that this problem can be addressed by using dilute magnetic semiconductor (DMS) contacts instead of metallic ones. We present the results of our optical experiments on a GaAs/AlGaAs diode fitted with a DMS spin injector contact. These measurements show a 90% spin polarization of the current in the semiconductor. Moreover, we describe a novel magnetoresistance effect based on the suppression of one of the spin channels in the semiconductor. This effect should allow the detection of a spin polarized current directly by magnetoresistance measurements.