Electrical spin injection into semiconductors

Electrical spin injection (i.e., injection of a spin-polarized current) into semiconductors has been a hot topic in semiconductor physics over the past few years. The reasons are obvious: spin injection would pave the way for a fully new class of electronic devices, in which the electronʹs spin, rather than its charge, is manipulated for information processing. Such devices could, e.g., combine the advantages of a magnetic hard-disk with semiconductor memory. Also, devices dissipating only minimal amounts of energy could be developed, and – because spin is an intrinsically quantum-mechanical property – spin devices could be used for a solid-state implementation of logical gates in a quantum computer. For many years, however, spin injection, usually approached by depositing ferromagnetic metallic contacts on a semiconductor, has remained elusive. We have now demonstrated spin injection into a semiconductor by using a II–VI-semiconductor spin aligner on top of a GaAs light-emitting diode. Spin injection was detected by determining the degree of circular polarization of the electroluminescence of the diode and was as high as 90%.