Multiband description of the optical properties of zincblende nitride quantum dots

We use the single-particle energies and wave functions calculated from an effective bond-orbital model and a microscopic empirical tight-binding model in combination with the configuration-interaction scheme to calculate the optical properties of cubic GaN/AlN quantum dots. Special attention is paid to the possible influence of the weak spin-orbit coupling on the optical spectra. The results are compared to recent experimental data. In agreement with the experiments, we find a strong polarization anisotropy of the excitonic transitions in the microscopic empirical tight-binding model, while the effective bond-orbital model misses this anisotropy in the absence of a piezoelectric field and an atomistic strain field. This missing anisotropy can be attributed to the artificially increased symmetry of the combined system of quantum dot geometry and underlying lattice structure.