Magneto-spectroscopy of excited states in charge-tunable GaAs/AlGaAs [111] quantum dots

TL;DR

This study combines experimental magneto-photoluminescence and theoretical modeling to analyze excited charge complexes in (111) GaAs/AlGaAs quantum dots, revealing unique emission patterns and detailed fine structure influenced by quantum dot symmetry.

Contribution

It provides the first detailed theoretical and experimental analysis of excited charge complexes in (111) GaAs/AlGaAs quantum dots, highlighting the effects of trigonal symmetry on their spectra.

Findings

Distinct emission patterns for excited complexes in (111) quantum dots

Accurate identification of charge states through combined experiment and theory

Extraction of exchange interaction constants and g-factors for excited states

Abstract

We present a combined experimental and theoretical study of highly charged and excited electron-hole complexes in strain-free (111) GaAs/AlGaAs quantum dots grown by droplet epitaxy. We address the complexes with one of the charge carriers residing in the excited state, namely, the ``hot'' trions X$^{-*}$ and X$^{+*}$, and the doubly negatively charged exciton X$^{2-}$. Our magneto-photoluminescence experiments performed on single quantum dots in the Faraday geometry uncover characteristic emission patterns for each excited electron-hole complex, which are very different from the photoluminescence spectra observed in (001)-grown quantum dots. We present a detailed theory of the fine structure and magneto-photoluminescence spectra of X$^{-*}$, X$^{+*}$ and X$^{2-}$ complexes, governed by the interplay between the electron-hole Coulomb exchange interaction and the heavy-hole mixing, characteristic for these quantum dots with a trigonal symmetry. Comparison between experiment and theory of the magneto-photoluminescence allows for precise charge state identification, as well as extraction of electron-hole exchange interaction constants and $g$-factors for the charge carriers occupying excited states.