Identification of electric dipole moments of excitonic complexes in nitride-based quantum dots

The built-in dipole moments of excitonic and multiexcitonic complexes of GaN/AlN quantum dots (charged and uncharged excitons and biexcitons) are investigated in detail, both experimentally and theoretically. The calculations are done with Hartree-Fock wave functions in the framework of an 8-band $\mathbf{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{p}$ approximation. Electric dipole moments of different excitonic complexes are found to vary significantly. Hence, their Coulomb coupling to charged defects in the vicinity of a QD produces emission energy variations, known as spectral diffusion, which can be used to identify the emitting excitonic complex. This method was exemplary applied to the presented cathodoluminescence and $\ensuremath{\mu}$-photoluminescence data and opens a way to identify excitonic complexes by their response to external electric fields.