2D–3D transitions in the quantum Stark effect in self-assembled InAs/GaAs quantum dots

In self-assembled quantum dots (SAD), the relation between the electric dipole moment arising from the electron–hole separation and the Stark shift takes different forms as a function of SAD shape and composition. This effect is attributed to the strain field distribution that strongly influences the rapidly varying confining potential for holes, and changes substantially with the dot morphology. In particular, truncated pyramidal or elongated lens-shaped SADs exhibit the normal linear dependence of the Stark shift on the electric dipole moment, thereby reflecting a 2D character in the electron–hole confinement. At the opposite, SADs with large aspect ratio between height and base, e.g., with pyramidal or hemispherical shapes, show significant deviations of the Stark shift from the normal linear dependence on the dipole moment. We point out that this absence of correlation between the Stark shift and electric dipole moment reflects a true 3D confinement in SADs.