Electrical spin injection using dilute magnetic semiconductors

Abstract

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 [1]. The reasons are obvious: spin injection would pave the way for an entirely new class of electronic devices, in which the electron's spin, rather than its charge is manipulated for information processing [2]. 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 several years different research groups have tried to achieve spin injection in top semiconductors from ferromagnetic metal contacts. Although careful experiments were performed, none of them showed convincing results [3,4]. This lack of success can be explained by a simple resistor model which shows that indeed a mismatch in conductivities prevents efficient spin injection in these systems. We have used a dilute magnetic II–VI-semiconductor as a spin aligner to inject highly spin polarized electrons into a GaAs light emitting diode. The circular polarization of the electroluminescence of the diode indicates that we indeed achieve up to 90% of electron spin polarization in our experiment and that DMSs are a class of materials which is highly promising for spin injection into semiconductors.