Electrical spin-injection into semiconductors-from cobalt contacts to semiconductor spin aligners

Injecting spin polarized electrons into a semiconductor has been a challenge during the past years. Using the spin information of the electron rather than its charge in a semiconductor device, would enable new device technologies or even new kinds of information processing techniques. However, while tunneling or all metal magnetoresistive devices are close to production state or already on the market, electrical spin-injection from ferromagnetic contacts into semiconductors has remained illusive. We have developed a theoretical model which explains the failure of former spin-injection experiments and which shows the way towards efficient spin-injection devices using semimagnetic semiconductor spin aligners. At the same time we have demonstrated experimentally the feasibility of spininjection using a dilute magnetic II–VI-semiconductor as a spin aligner. A spin polarized current was injected into a GaAs/AlGaAs light emitting diode, and the spin polarization was detected via the optical circular polarization of the electroluminescence signal of the diode.