The Silicon Inversion Layer With A Ferromagnetic Gate: A Novel Spin Source

TL;DR

This paper proposes a novel silicon transistor design with a ferromagnetic gate that enables control over spin-polarized and pure spin currents, showing potential for high magnetoresistance effects.

Contribution

It introduces a new spin transport mechanism in silicon transistors using ferromagnetic gates, enabling high spin polarization and magnetoresistance.

Findings

Potential to generate 100% spin-polarized currents

Ability to produce pure spin currents without net charge flow

Magnetoresistance ratios can be arbitrarily large at low bias

Abstract

Novel spin transport behavior is theoretically shown to result from replacing the usual metal (or poly-silicon) gate in a silicon field-effect transistor with a ferromagnet, separated from the semiconductor by an ultra-thin oxide. The spin-dependent interplay between the drift current (due to a source-drain bias) and the diffusion current (due to carrier leakage into the ferromagnetic gate) results in a rich variety of spin dependence in the current that flows through such a device. We examine two cases of particular interest: (1) creating a 100% spin-polarized electrical current and (2) creating a pure spin current without a net electrical current. A spin-valve consisting of two sequential ferromagnetic gates is shown to exhibit magnetoresistance dependent upon the relative orientations of the magnetization of the two ferromagnets. The magnetoresistance ratio grows to arbitrarily large values in the regime of low source-drain bias, and is limited only by the spin-flip time in the channel.