Electrical spin-injection into silicon from a ferromagnetic metal/tunnel barrier contact

Abstract

The electrons spin angular momentum is one of several alternative state variables under consideration on the International Technology Roadmap for Semiconductors (ITRS) for processing information in the fundamentally new ways that will be required beyond the ultimate scaling limits of silicon-based complementary metal-oxide-semiconductor technology. Electrical injection/transport of spin-polarized carriers is prerequisite for developing such an approach. Although significant progress has been realized in GaAs (ref.4), little progress has been made in Si, despite its overwhelming dominance of the semiconductor industry. Here, we report successful injection of spin-polarized electrons from an iron film through an Al"2O"3 tunnel barrier into Si(001). The circular polarization of the electroluminescence resulting from radiative recombination in Si and in GaAs (in Si/AlGaAs/GaAs structures) tracks the Fe magnetization, confirming that these spin-polarized electrons originate from the Fe contact. The polarization reflects Fe majority spin. We determine a lower bound for the Si electron spin polarization of 10, and obtain an estimate of 30 at 5K, with significant polarization extending to at least 125K. We further demonstrate spin transport across the Si/AlGaAs interface. © 2007 Nature Publishing Group.