Strain and band-mixing effects on the excitonic Aharonov-Bohm effect in In(Ga)As/GaAs ringlike quantum dots

TL;DR

This study investigates how strain and band-mixing influence the excitonic Aharonov-Bohm effect in ringlike In(Ga)As/GaAs quantum dots, revealing enhanced oscillations due to strain effects and inner layer coverage.

Contribution

It introduces a detailed model combining strain distribution and multiband Hamiltonian to analyze excitonic AB oscillations in strained quantum dots with complex shapes.

Findings

Strain doubles the amplitude of excitonic AB oscillations.

Inner layer coverage enhances AB oscillations by localizing holes.

Computed oscillations match recent experimental measurements.

Abstract

Neutral excitons in strained axially symmetric In(Ga)As/GaAs quantum dots with ringlike shape are investigated. Similar to experimental self-assembled quantum rings, the analyzed quantum dots have volcano-like shapes. The continuum mechanical model is employed to determine the strain distribution, and the single-band envelope function approach is adopted to compute the electron states. The hole states are determined by the axially symmetric multiband Luttinger-Kohn Hamiltonian, and the exciton states are obtained from an exact diagonalization. We found that the presence of the inner layer covering the ring opening enhances the excitonic Aharonov-Bohm (AB) oscillations. The reason is that the hole becomes mainly localized in the inner part of the quantum dot due to strain, whereas the electron resides mainly inside the ring-shaped rim. Interestingly, larger AB oscillations are found in the analyzed quantum dot than in a fully opened quantum ring of the same width. Comparison with the unstrained ring-like quantum dot shows that the amplitude of the excitonic Aharonov-Bohm oscillations are almost doubled in the presence of strain. The computed oscillations of the exciton energy levels are comparable in magnitude to the oscillations measured in recent experiments.