Electrical spin injection in a ferromagnetic semiconductor heterostructure

Conventional electronics is based on the manipulation of electronic charge. An intriguing alternative is the field of ‘spintronics’, wherein the classical manipulation of electronic spin in semiconductor devices gives rise to the possibility of reading and writing non-volatile information through magnetism. Moreover, the ability to preserve coherent spin states in conventional semiconductors and quantum dots may eventually enable quantum computing in the solid state. Recent studies have shown that optically excited electron spins can retain their coherence over distances exceeding 100 micrometres (ref. 7). But to inject spin-polarized carriers electrically remains a formidable challenge. Here we report the fabrication of all-semiconductor, light-emitting spintronic devices using III–V heterostructures based on gallium arsenide. Electrical spin injection into a non-magnetic semiconductor is achieved (in zero magnetic field) using a p-type ferromagnetic semiconductor as the spin polarizer. Spin polarization of the injected holes is determined directly from the polarization of the emitted electroluminescence following the recombination of the holes with the injected (unpolarized) electrons.