Strain-energy distribution and electronic structure of InAs pyramidal quantum dots with uncovered surfaces: Tight-binding analysis

The strain energy distribution and electronic structure of InAs pyramidal quantum dots (QD’s) with uncovered surfaces have been analyzed theoretically. The strain in the QD’s, which simulate self-assembled QD’s on GaAs, is calculated using the Keating potential. The strain energy per inside atom is largest at the lowest layer, while the several layers near the pyramid top have practically no strain. Using the ${\mathrm{sp}}^3{s}^{*}$ tight-binding method, we calculate the densities of states for the inside states and the surface states. The density of the inside states shows a large energy gap; $2.71–1.74$ eV for $161–1222$-atom QD’s. At the same time, we find the surface states in the gap.