Semiconductors between spin-polarized source and drain

TL;DR

This paper reviews the challenges of spin transport in semiconductors and discusses how to optimize interface resistance to preserve spin signals, highlighting differences between carbon nanotubes and semiconductors.

Contribution

It provides a comprehensive analysis of spin injection and transport conditions in nonmagnetic channels, with experimental insights and suggestions for improving spin signal detection in semiconductors.

Findings

Carbon nanotubes more effectively convert spin information into electrical signals.

Optimal interface resistance is crucial for maintaining spin signals.

Challenges in semiconductors stem from dwell time and spin lifetime constraints.

Abstract

Injecting spins into a semiconductor channel and transforming the spin information into a significant electrical output signal is a long standing problem in spintronics. Actually, this is the prerequisite of several concepts of spin transistor. In this tutorial article, we discuss the general problem of spin transport in a nonmagnetic channel between source and drain. Two problems must be mastered: i) In the diffusive regime, the injection of a spin polarized current from a magnetic metal beyond the ballistic transport zone requires the insertion of a spin dependent and large enough interface resistance. ii) In both the diffusive and ballistic regimes, and whatever the metallic or semiconducting character of the source/drain, a small enough interface resistance is the condition to keep the dwell time shorter than the spin lifetime and thus to conserve the spin accumulation-induced output signal at an optimum level. Practically, the main difficulties come from the second condition. In our presentation of experimental results, we show why the transformation of spin information into a large electrical signal has been more easily achieved with carbon nanotubes than with semiconductors and we discuss how the situation could be improved in the later case.