Strain distribution and electronic structure of InAs quantum dots on GaAs: Atomic scale calculations

We have theoretically investigated the strain distribution and electronic structure of InAs pyramidal quantum dots (QDs) using the Keating potential and the sp(3)s* tight-binding method. 161-, 1222-, and 4047-atom QDs on GaAs with no cap layers are studied. We find that the strain energy (averaged over a layer) is largest at the QD base layer and decreases rapidly with increasing distance from the base. We have calculated the electronic states and their energies in the QDs, and obtained the densities of states for the "inside" states and the surface states separately. The density of the "inside" states shows a large gap (2.71 eV in the 161-atom QD, and 1.74 eV in the 1222-atom QD) due to the strong confinement effect of the QD. At the same time, we find a high density of surface states in the gap due to the, large number of surface atoms in the QDs.