Bias-controlled sensitivity of ferromagnet/semiconductor electrical spin detectors

TL;DR

This study demonstrates that the sensitivity of ferromagnet/semiconductor electrical spin detectors can be extensively tuned using voltage bias, affecting both magnitude and sign, with implications for spintronic device optimization.

Contribution

We reveal that bias voltage influences spin detection sensitivity through interface tunneling properties and semiconductor electric fields, enabling control over sensitivity sign and magnitude.

Findings

Sensitivity can be tuned over a wide range with bias voltage.

Bias can induce positive or negative voltage responses.

Detection sensitivity can be enhanced ten-fold.

Abstract

Using Fe/GaAs Schottky tunnel barriers as electrical spin detectors, we show that the magnitude and sign of their spin-detection sensitivities can be widely tuned with the voltage bias applied across the Fe/GaAs interface. Experiments and theory establish that this tunability derives not just simply from the bias dependence of the tunneling conductances $G_{\uparrow,\downarrow}$ (a property of the interface), but also from the bias dependence of electric fields in the semiconductor which can dramatically enhance or suppress spin-detection sensitivities. Electrons in GaAs with fixed polarization can therefore be made to induce either positive or negative voltage changes at spin detectors, and some detector sensitivities can be enhanced over ten-fold compared to the usual case of zero-bias spin detection.