Theory for optical properties of nitride-based quantum dot systems

The influence of structural properties and interaction-induced effects on optical spectra of self-assembled Nitride-based quantum-dot (QD) systems is analyzed within a microscopic theory. Beside the QDs, the wetting-layer (WL) plays an important role for laser applications since it is involved in the carrier generation and scattering processes, which modify the optical properties of the QDs. The single-particle properties are determined on an atomistic level from tight-binding calculations. Coulomb interaction effects and carrier-phonon interaction are considered in a second step to study excitation-induced effects for elevated carrier densities at room temperature. Numerical results are presented for InN/GaN QD-WL systems. Nearly degenerate top valence-subbands lead to strong subband mixing. We also find modified dipole selection rules with a dark ground state exciton and rather strong excitation-induced line shifts of the QD transitions in addition to the excitation-induced line-broadening. While these results are masked in conventional lasers due to strong inhomogeneous broadening, they are directly relevant for the application of QDs in microcavity lasers.