On the origin of the blueshift from type-II quantum dots emission using microphotoluminescence

We have studied type-II InP/GaAs self-assembled quantum dots by microphotoluminescence spectroscopy. Sharp spectral features were observed on top of a broad emission band. They are associated to statistical fluctuations from the ensemble of dots. Photoluminescence measurements as a function of the excitation intensity revealed markedly distinct behaviors: the broadband contour shows a large blueshift while the energy positions of the sharp features remain basically constant. We show that the large blueshift of the broad emission band in type-II quantum dots is not due to the barrier interface potential variation, but to the state filling of higher-energy states.