Non-local opto-electrical spin injection and detection in germanium at room temperature

TL;DR

This paper demonstrates room-temperature non-local spin injection and detection in germanium using electrical and optical methods, advancing spintronic device capabilities compatible with existing silicon technology.

Contribution

It introduces pure spin current injection and detection in germanium at room temperature using both electrical and optical techniques, expanding opto-spintronic device options.

Findings

Pure spin currents achieved in germanium at room temperature.

Electrical and optical injection methods demonstrated.

Detection via MTJ and inverse spin-Hall effect confirmed.

Abstract

Non-local carrier injection/detection schemes lie at the very foundation of information manipulation in integrated systems. This paradigm consists in controlling with an external signal the channel where charge carriers flow between a "source" and a well separated "drain". The next generation electronics may operate on the spin of carriers instead of their charge and germanium appears as the best hosting material to develop such a platform for its compatibility with mainstream silicon technology and the long electron spin lifetime at room temperature. Moreover, the energy proximity between the direct and indirect bandgaps allows for optical spin injection and detection within the telecommunication window. In this letter, we demonstrate injection of pure spin currents (\textit{i.e.} with no associated transport of electric charges) in germanium, combined with non-local spin detection blocks at room temperature. Spin injection is performed either electrically through a magnetic tunnel junction (MTJ) or optically, exploiting the ability of lithographed nanostructures to manipulate the distribution of circularly-polarized light in the semiconductor. Pure spin current detection is achieved using either a MTJ or the inverse spin-Hall effect (ISHE) across a platinum stripe. These results broaden the palette of tools available for the realization of opto-spintronic devices.