It is demonstrated that the photoluminescence spectra of single self-assembled quantum dots are very sensitive to the experimental conditions, such as excitation energy and crystal temperature. A qualitative explanation is given in terms of the effective diffusion of the photogenerated carriers, determined by the experimental conditions, which influence the capture probability and hence also the charge state of the quantum dots. This is proposed as an effective tool to populate single quantum dots with extra electrons, by purely optical means, in order to study phenomena involving charged excitons.

One of the authors (E.S.M.) gratefully acknowledges ¢nancial support of the Swedish Institute within the Visby Programme and partial support of the Russian Academy of Sciences (Low-Dimensional Nanostructures 2001).

3 páginas, 3 figuras.-- PACS: 78.67.He, 71.35.-y, 78.55.Cr

Peer reviewed