Injection and detection of spin in a semiconductor by tunneling via interface states

TL;DR

This paper analyzes how spin injection and detection in semiconductors are affected by interface states, showing that localized states can enhance spin accumulation and that detection primarily probes the semiconductor channel.

Contribution

It introduces a model considering both direct tunneling and tunneling via interface states, revealing that interface states can enhance spin accumulation without suppressing it.

Findings

Spin accumulation is genuinely enhanced by interface states.

Detected spin signals mainly reflect the semiconductor channel.

Localized states do not suppress but can amplify spin signals.

Abstract

Injection and detection of spin accumulation in a semiconductor having localized states at the interface is evaluated. Spin transport from a ferromagnetic contact by sequential, two-step tunneling via interface states is treated not in itself, but in parallel with direct tunneling. The spin accumulation induced in the semiconductor channel is not suppressed, as previously argued, but genuinely enhanced by the additional spin current via interface states. Spin detection with a ferromagnetic contact yields a weighted average of the spin accumulation in the channel and in the localized states. In the regime where the spin accumulation in the localized states is much larger than that in the channel, the detected spin signal is insensitive to the spin accumulation in the localized states and the ferromagnet probes the spin accumulation in the semiconductor channel.