Precise measurement of the fraction of charged dots in self-assembled quantum dot ensembles using ultrafast pump-probe techniques

We demonstrate that polarization-resolved ultrafast pump-probe spectroscopy can be used to measure accurately (<10%) the fraction of charged dots in quantum dot (QD) ensembles. The method is applied to study the dependence of charging levels in thermally annealed InGaAs QDs, grown both as nominally undoped and n-type modulation-doped structures. We also show that the method can be used to study the spectral distribution of charges (or charging profiles) in quantum dot ensembles.

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