Using Light to Polarize and Detect Electron Spins in Silicon

TL;DR

This paper demonstrates all-optical methods to detect and analyze electron and exciton spin properties in bulk silicon, revealing new insights into spin relaxation and optical selection rules through luminescence polarization measurements.

Contribution

It provides the first direct optical measurement of electron spin relaxation and optical selection rules in silicon, including for free excitons, using luminescence polarization techniques.

Findings

Determined optical selection rules for phonon-assisted transitions in silicon.

Measured electron spin relaxation times in silicon under new conditions.

Explored spin properties of free excitons in silicon.

Abstract

Despite decades of research, demonstration of all-optical detection and control of free electron spins in silicon remains elusive. Here, we directly probe the electron spin properties in bulk silicon by measuring the polarization of luminescence following circularly polarized light excitation. The experiments performed for both direct and indirect gap excitation allow not only an experimental determination of the optical selection rules in silicon for the different phononassisted transitions but they also lead to the measurement of the spin relaxation of electrons in conditions which are not accessible using transport techniques. We also measure the spin properties of free excitons in bulk silicon, a very little explored field.