New results on the origin of the emission from type-Ⅱquantum dots using micro-photoluminescence

摘要

We studied type-Ⅱ InP/ GaAs self-assembled quantum dots by micro- microphotoluminescencespectroscopy. Sharp spectral features were observed on topphotoluminescence of a broad emission band. They are associated to exciton emission lines inindividual dots belonging to an ensemble with statistical fluctuations of dotsizes. Photoluminescence measurements as a function of the excitationintensity revealed markedly distinct behaviors: the broad band contour shows alarge blue shift while the energy positions of the sharp features remainbasically constant. We have strong evidence that the large blue shift of thebroad emission band in type-Ⅱ quantum dots is not due to the band-bendingeffect, but to the filling of higher energy states.