We investigate the vertical electric field tuning of the exciton fine-structure splitting (FSS) in several InGaAs and GaAs quantum dots (QDs) using the atomistic empirical pseudopotential approach and configuration interaction. We find that the FSS is surprisingly tunable, with a rate similar to the one reported for lateral electric fields. The minimum FSS for GaAs QDs often lies below the radiative linewidth, which makes them good candidates for the generation of entangled photon pairs. We highlight, however, that random alloy fluctuations affect the minimum FSS by $\pm$1.4 $\mu$eV, so that a postselection of QDs may still be beneficial to obtain entangled photon pairs with the highest fidelity. We suggest a simple experimental procedure for this task. The FSS is therefore a rare observable, where the specific decoration of the random alloy lattice matters significantly.

• Received 13 July 2012

DOI:https://doi.org/10.1103/PhysRevB.86.161302