Spin and energy relaxation in germanium studied by spin-polarized direct-gap photoluminescence
Abstract
Spin orientation of photoexcited carriers and their energy relaxation is investigated in bulk Ge by studying spin-polarized recombination across the direct band gap. The control over parameters such as doping and lattice temperature is shown to yield high polarization degree, namely larger than 40%, as well as a fine-tuning of the angular momentum of the emitted light with a complete reversal between right- and left-handed circular polarization. By combining the measurement of the optical polarization state of band-edge luminescence and Monte Carlo simulations of carrier dynamics, we show that these very rich and complex phenomena are the result of the electron thermalization and cooling in the multi-valley conduction band of Ge. The circular polarization of the direct-gap radiative recombination is indeed affected by energy relaxation of hot electrons via the X valleys and the Coulomb interaction with extrinsic carriers. Finally, thermal activation of unpolarized L valley electrons accounts for the luminescence depolarization in the high temperature regime.
Keywords
Cite
@article{arxiv.1305.4024,
title = {Spin and energy relaxation in germanium studied by spin-polarized direct-gap photoluminescence},
author = {F. Pezzoli and L. Qing and A. Giorgioni and G. Isella and E. Grilli and M. Guzzi and H. Dery},
journal= {arXiv preprint arXiv:1305.4024},
year = {2013}
}