Influence of symmetry and Coulomb-correlation effects on the optical properties of nitride quantum dots

TL;DR

This study investigates how symmetry and Coulomb interactions influence the optical properties of InN/GaN quantum dots, revealing size-dependent emission behaviors and the effects of quantum confinement and Stark effect.

Contribution

It combines tight-binding and configuration interaction methods to analyze multi-exciton spectra and provides analytical insights into the effects of symmetry and Coulomb interactions.

Findings

Small QDs show vanishing exciton and biexciton ground state emission.

Larger QDs exhibit bright ground state emission with reduced oscillator strength.

Quantum confined Stark effect significantly impacts optical spectra in larger QDs.

Abstract

The electronic and optical properties of self-assembled InN/GaN quantum dots (QDs) are investigated by means of a tight-binding model combined with configuration interaction calculations. Tight-binding single particle wave functions are used as a basis for computing Coulomb and dipole matrix elements. Within this framework, we analyze multi-exciton emission spectra for two different sizes of a lens-shaped InN/GaN QD with wurtzite crystal structure. The impact of the symmetry of the involved electron and hole one-particle states on the optical spectra is discussed in detail. Furthermore we show how the characteristic features of the spectra can be interpreted using a simplified Hamiltonian which provides analytical results for the interacting multi-exciton complexes. We predict a vanishing exciton and biexciton ground state emission for small lens-shaped InN/GaN QDs. For larger systems we report a bright ground state emission but with drastically reduced oscillator strengths caused by the quantum confined Stark effect.