Single dot spectroscopy on InAs/GaAs piezoelectric quantum dots

We report on single dot spectroscopy of InAs/GaAs quantum dots grown by molecular beam epitaxy along the polar (211)B direction. Unlike the (001) dots, in the (211)B dots we have systematically observed large blue shifts of the biexciton lines with respect to the excitonic ones. This is attributed to the strong piezoelectric field present inside the polar dots. In order to better interpret our results, we performed preliminary photoluminesence studies under the influence of an external electric field, which showed large Stark shifts of the quantum dot ensemble. From the analysis of these results, we deduced that the piezoelectric field in the (211)B InAs/GaAs quantum dots is as large as 800 kV/cm, which is consistent with the large anti-binding energies of bi-excitons observed in this system. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)