Impact of ex-situ rapid thermal annealing on the magneto-optical properties and the oscillator strength of In(Ga)As quantum dots

TL;DR

This study shows that rapid thermal annealing significantly enhances the magneto-optical properties and oscillator strength of In(Ga)As quantum dots, with optimal annealing increasing oscillator strength by over twofold.

Contribution

It demonstrates how rapid thermal annealing modifies quantum dot properties, leading to increased oscillator strength and altered magneto-optical behavior, which was not previously quantified.

Findings

Annealing at 850°C doubles the oscillator strength of InAs/GaAs quantum dots.

Magneto-optical properties are strongly influenced by annealing-induced shape and composition changes.

Emission lifetime increases with quantum dot volume, correlating with oscillator strength enhancements.

Abstract

We discuss the influence of a rapid thermal annealing step on the magneto-optical emission properties of In(Ga)As/GaAs quantum dots. We map out a strong influence of the growth- and anneling parameters on the quantum excitons' effective Land\'e g-factors and in particular on their diamagnetic coefficients, which we directly correlate with the modification of the emitters shape and material composition. In addition, we study the excitons' spontaneous emission lifetime as a function of the annealing temperature and the dot height, and observe a strong increase of the emission rate with the quantum dot volume. The corresponding increase in oscillator strenth yields fully consistent results with the analysis of the diamagenic behavior. In particular, we demonstrate that a rapid thermal annealing step of 850$^\circ$ C can be employed to increase the oscillator strength of as-grown InAs/GaAs QDs by more than a factor of $2$.