Excitation transfer in vertically self-organized pairs of unequal-sized InAs/GaAs quantum dots

The excitation transfer processes in vertically self organized pairs of une qual-sized quantum dots (QD's), which are created in InAs/GaAs bilayers wit h different InAs deposition amounts in the first and second layers, have be en investigated experimentally by photoluminescence technique. The distance between the two dot layers is varied from 3 to 12 nm. The optical properti es of the formed pairs of unequal-sized QD's with clearly discernible groun d-state transition energy depend on the spacer thickness. When the spacer l ayer of GaAs is thin enough, only one photoluminescence peak related to the large QD ensemble has been observed as a result of strong electronic coupl ing in the InAs QD pairs. The results provide evidence for nonresonant ener gy transfer from the smaller QDs in the second layer to the larger QD's in the first layer in such an asymmetric QD pair.