Observation of dip structures in PLE spectra of a highly excited single self-assembled quantum dot

We have observed dip structures in photoluminescence excitation (PLE) spectra of a highly excited single InGaAs/GaAs self-assembled quantum dot. Some of the exciton PLE peaks lying in continuum states turn into the dips with increasing excitation power. The most remarkable feature is that the biexciton-PLE shows peaks at the excitation energies where the exciton PLE shows the dip structures. Using a model based on the excitation power dependence of the photoluminescence intensity, we discuss the origin of the dip structures.