Strain effects on the electronic structure of strongly coupled self-assembled $\mathrm{InAs}∕\mathrm{GaAs}$ quantum dots: Tight-binding approach

Strain effects on the electronic structure of strongly coupled self-assembled $InAs ∕ GaAs$ quantum dots: Tight-binding approach

W. Jaskólski, M. Zieliński, Garnett W. Bryant, and J. Aizpurua

Phys. Rev. B 74, 195339 – Published 29 November 2006

Abstract

We present an atomistic tight-binding study of the electronic structure and optical properties of vertically stacked, double, self-assembled, $InAs ∕ GaAs$ quantum dots. The investigated dots are lens-shaped and are situated on wetting layers. We study coupling and strain effects for closely spaced dots. For intermediate separation distances between the dots, the tight-binding theory confirms the effect of strain-induced localization of the ground hole state in the lower dot, as predicted in other approaches. However, the tight-binding calculations predict weaker localization at large separation distances and no localization for closely spaced and overlapping dots, which have not been investigated so far. An anomalous reversal of the bonding character of the ground hole state for large separation distances, found previously by us for unstrained systems, is present also for strained dots. We also show that in double quantum dots there may exist bound and localized electron and hole states with energies above the edge of the wetting layer continuum. The calculated redshift of the lowest optical transition for decreasing distance between the interacting dots agrees qualitatively with experimental data.