Electron-Hole Correlations and Optical Excitonic Gaps in Quantum-Dot Quantum Wells: Tight-Binding Approach

TL;DR

This paper models electron-hole interactions in quantum-dot quantum wells using an empirical tight-binding approach, accurately predicting excitonic gaps and Coulomb effects consistent with experimental data.

Contribution

It introduces a detailed tight-binding model incorporating Coulomb and exchange interactions to accurately compute excitonic properties in QDQWs.

Findings

Coulomb shifts of ~100 meV in QDQWs

Exchange splittings of ~1 meV observed

Calculated optical gaps agree with experiments

Abstract

Electron-hole correlation in quantum-dot quantum wells (QDQW's) is investigated by incorporating Coulomb and exchange interactions into an empirical tight-binding model. Sufficient electron and hole single-particle states close to the band edge are included in the configuration to achieve convergence of the first spin-singlet and triplet excitonic energies within a few meV. Coulomb shifts of about 100 meV and exchange splittings of about 1 meV are found for CdS/HgS/CdS QDQW's (4.7 nm CdS core diameter, 0.3 nm HgS well width and 0.3 nm to 1.5 nm CdS clad thickness) which have been characterized experimentally by Weller and co-workers [ D. Schooss, A. Mews, A. Eychmuller, H. Weller, Phys. Rev. B, 49, 17072 (1994)]. The optical excitonic gaps calculated for those QDQW's are in good agreement with the experiment.