Enhanced phonon-assisted absorption in single InAs/GaAs quantum dots

Exciton-longitudinal optic-phonon coupling in InAs/GaAs quantum dots is investigated by means of single-dot spectroscopy. Photoluminescence spectra in the excitonic ground-state region exhibit a series of new emission lines which we ascribe to single exciton recombination perturbed by charged defects close to the dot. Compared to unperturbed excitonic recombination, the resulting dipole in these complexes leads to enhanced coupling to LO phonons in photoluminescence excitation spectra. Evidence for resonant enhancement of phonon-assisted processes in absorption is also presented.