Atomic scale calculations for strain distribution and electronic structure of InAs pyramidal quantum dots on (100) GaAs

The theoretical investigations for the strain distribution and electronic structure of InAs pyramidal quantum dots (QDs) have been performed using the Keating potential and the sp(3)s* tight-binding method. The 161-, 1222-, and 4047-atom QDs on GaAs with no cap layers are studied. The strain energy is largest at the QD base layer and decreases rapidly with increasing distance from the base. We have calculated the energies, the wave function "inside" fractions, and the densities of states for the inside states and the surface states. The density of the inside states shows a large energy gap [2.71 eV (161-atom QD), 1.74 eV (1222-atom QD)] due to the strong confinement effect. We find the surface states from the {111}As facets, (100)In base, and {111}In facets of the QDs, which are distributed in the different energy regions in the gap.