Optical spectroscopy of single quantum dot molecules under applied electric field

The photoluminescence spectrum of individual pairs of vertically stacked InAs quantum dots is investigated as a function of an external electric field along the growth direction. Comparing samples with different inter-dot distances, we find for the case of the closest pairs clear experimental evidences of single carrier transfer from one dot to the other, with a transfer rate that is controlled by the applied voltage. We model the spectra with a theoretical calculation, which takes into account both the field-dependent carrier kinetics and the many-body interactions in the quantum dot molecule.