Exciton lifetime and emission polarization dispersion in strongly in-plane asymmetric nanostructures

TL;DR

This study investigates how structural asymmetry in elongated quantum dots affects exciton recombination and emission polarization, revealing a transition from strong to weak confinement regimes and their influence on optical properties.

Contribution

It provides a combined experimental and theoretical analysis of exciton dynamics and polarization in asymmetric nanostructures, especially elongated quantum dots with tunable confinement.

Findings

Transition from strong to weak confinement regimes in quantum dots.

Emission polarization depends on structural asymmetry and excitation conditions.

Proposed method to determine intrinsic polarization-dependent exciton coupling.

Abstract

We present experimental and theoretical investigation of exciton recombination dynamics and the related polarization of emission in highly in-plane asymmetric nanostructures. Considering general asymmetry- and size-driven effects, we illustrate them with a detailed analysis of InAs/AlGaInAs/InP elongated quantum dots. These offer a widely varied confinement characteristics tuned by size and geometry that are tailored during the growth process, which leads to emission in the application-relevant spectral range of 1.25-1.65 {\mu}m. By exploring the interplay of the very shallow hole confining potential and widely varying structural asymmetry, we show that a transition from the strong through intermediate to even weak confinement regime is possible in nanostructures of this kind. This has a significant impact on exciton recombination dynamics and the polarization of emission, which are shown to depend not only on details of the calculated excitonic states but also on excitation conditions in the photoluminescence experiments. We estimate the impact of the latter and propose a way to determine the intrinsic polarization-dependent exciton light-matter coupling based on kinetic characteristics.