Influence of Trapping on the Exciton Dynamics of Al_xGa_1-xAs Films

TL;DR

This study investigates how trapping influences exciton relaxation in high purity AlGaAs films, revealing a non-monotonic relationship between excitation density and photoluminescence dynamics, modulated by alloy composition and temperature.

Contribution

It introduces a phenomenological four-level model that describes the impact of exciton localization on relaxation dynamics in AlGaAs epilayers.

Findings

t_max depends non-monotonically on excitation density

Exciton localization is enhanced by higher Al content

Localization effects diminish above certain temperature thresholds

Abstract

We present a systematic study on the exciton relaxation in high purity AlGaAs epilayers. The time for the excitonic photoluminescence to reach its maximum intensity (t_max) shows a non-monotonic dependence on excitation density which is attributed to a competition between exciton localization and carrier-carrier scattering. A phenomenological four level model fully describes the influence of exciton localization on t_max. This localization effect is enhanced by the increase of the Al content in the alloy and disappears when localization is hindered by rising the lattice temperature above the exciton trapping energy.