Effect of quantum confinement on exciton-phonon interactions

TL;DR

This study examines how quantum confinement affects exciton-phonon interactions in GaAs/AlAs superlattices, revealing reduced exciton-environment interactions with increased localization but enhanced LO-phonon coupling.

Contribution

It provides detailed measurements of exciton linewidths and phonon interactions in localized states, highlighting the impact of dimensionality and local structure.

Findings

Low-temperature linewidth is five times smaller than in Q2D excitons.

Exciton-acoustic-phonon interaction coefficient is 5-6 times smaller.

Localization enhances exciton-LO-phonon interaction, sensitive to local structure.

Abstract

We investigate the homogeneous linewidth of localized type-I excitons in type-II GaAs/AlAs superlattices. These localizing centers represent the intermediate case between quasi-two-dimensional (Q2D) and quasi-zero-dimensional localizations. The temperature dependence of the homogeneous linewidth is obtained with high precision from micro-photoluminescence spectra. We confirm the reduced interaction of the excitons with their environment with decreasing dimensionality except for the coupling to LO-phonons. The low-temperature limit for the linewidth of these localized excitons is five times smaller than that of Q2D excitons. The coefficient of exciton-acoustic-phonon interaction is 5 ~ 6 times smaller than that of Q2D excitons. An enhancement of the average exciton-LO-phonon interaction by localization is found in our sample. But this interaction is very sensitive to the detailed structure of the localizing centers.