Coupled InAs/GaAs quantum dots with well-defined electronic shells

Artificial molecules are studied using coupled quantum-dot (QD) ensembles with well-defined electronic shells. The coupling strength between the zero-dimensional states is varied by changing the distance between two layers of stacked self-assembled InAs/GaAs QDs. For strongly coupled QDs grown with a 4 nm spacer, state-filling spectroscopy reveals a shift of the QD symmetric state to lower energies by similar to 23 meV. The wetting layer states are also strongly coupled because of the shallow confinement, resulting in a redshift of its symmetric state by similar to 26 meV. (C) 2000 American Institute of Physics. [S0003-6951(00)05416-4].