Optical orientation of electron spins and valence band spectroscopy in germanium

TL;DR

This study explores optical spin orientation and valence band spectroscopy in germanium, revealing how doping and electron transfer influence spin polarization and providing a new spectroscopic method for analyzing hole energy spectra.

Contribution

It introduces a novel optical spectroscopy approach to study spin polarization and hole energy spectra in germanium, highlighting the effects of doping and electron transfer.

Findings

Spin polarization varies from 30% to -60% with excitation energy.

Resonant electronic Raman scattering reveals inter-valence band excitations.

Provides a versatile method for analyzing hole energy spectra.

Abstract

We have investigated optical orientation in the vicinity of the direct gap of bulk germanium. The electron spin polarization is studied via polarization-resolved photoluminescence excitation spectroscopy unfolding the interplay between doping and ultrafast electron transfer from the center of the Brillouin zone towards its edge. As a result, the direct-gap photoluminescence circular polarisation can vary from 30% to -60% when the excitation laser energy increases. This study provides also simultaneous access to the resonant electronic Raman scattering due to inter-valence band excitations of spin-polarized holes, yielding a fast and versatile spectroscopic approach for the determination of the energy spectrum of holes in semiconducting materials.