Electron–hole bilayer quantum dots: phase diagram and exciton localization

We studied a vertical ‘quantum dot molecule’, where one of the dots is occupied by electrons and the other by holes. We find that different phases occur in the ground state, depending on the carrier density and the interdot distance. When the system is dominated by shell structure, orbital degeneracies can be removed either by Hundʹs rule, or by Jahn–Teller deformation. Both mechanisms can lead to a maximum of the addition energy at mid-shell. At low densities and large interdot distances, bound electron–hole pairs are formed.