Theoretical analysis of electron-hole alignment in InAs-GaAs quantum dots

We present a theoretical analysis of the mean electron and hole positions in self-assembled InAs-GaAs quantum-dot structures. Because of the asymmetric dot shape, the electron center of mass should be displaced with respect to the hole center of mass in such dots, giving rise to a built-in dipole moment. Theoretical calculations on ideal pyramidal dots predict the electron to be localized above the hole, contrary to the results of recent Stark-effect spectroscopy. We use an efficient plane-wave envelope-function technique to determine the ground-state electronic structure of a range of dot models. In this technique, the Hamiltonian matrix elements due to all components of the potential are determined using simple analytical expressions. We demonstrate that the experimental data are consistent with a truncated dot shape and graded composition profile, with indium aggregation at the top surface of the dot.