Spin-polarized Tunneling in Hybrid Metal-Semiconductor Magnetic Tunnel Junctions

TL;DR

This paper demonstrates efficient spin-polarized tunneling in hybrid metal-semiconductor magnetic tunnel junctions, revealing significant magnetoresistance and detailed barrier characteristics, advancing spin injection technologies.

Contribution

It introduces a novel epitaxial magnetic tunnel junction with high tunneling magnetoresistance between MnAs and GaMnAs, providing insights into barrier properties and spin injection efficiency.

Findings

Tunneling magnetoresistance up to 30% at low temperatures.

Asymmetric tunnel barrier characterized through I-V analysis.

Presence of a correlation gap indicated by conductance behavior.

Abstract

We demonstrate efficient spin-polarized tunneling between a ferromagnetic metal and a ferromagnetic semiconductor with highly mismatched conductivities. This is indicated by a large tunneling magnetoresistance (up to 30%) at low temperatures in epitaxial magnetic tunnel junctions composed of a ferromagnetic metal (MnAs) and a ferromagnetic semiconductor (GaMnAs) separated by a nonmagnetic semiconductor (AlAs). Analysis of the current-voltage characteristics yields detailed information about the asymmetric tunnel barrier. The low temperature conductance-voltage characteristics show a zero bias anomaly and a V^1/2 dependence of the conductance, indicating a correlation gap in the density of states of GaMnAs. These experiments suggest that MnAs/AlAs heterostructures offer well characterized tunnel junctions for high efficiency spin injection into GaAs.