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

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 multiexciton 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 multiexciton 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.