We present an atomistic investigation of the influence of strain on the electronic properties of quantum dots ͑QD's͒ within the empirical sp 3 s* tight-binding ͑ETB͒ model with interactions up to second nearest neighbors and spin-orbit coupling. Results for the model system of capped pyramid-shaped InAs QD's in GaAs, with supercells containing ϳ10 5 atoms are presented and compared with previous empirical pseudopotential results. The good agreement shows that ETB is a reliable alternative for an atomistic treatment. The strain is incorporated through the atomistic valence-force field model. The ETB treatment allows for the effects of bond length and bond angle deviations from the ideal InAs and GaAs zinc-blende structure to be selectively removed from the electronic-structure calculation, giving quantitative information on the importance of strain effects on the bound-state energies and on the physical origin of the spatial elongation of the wave functions. Effects of dot-dot coupling have also been examined to determine the relative weight of both strain field and wavefunction overlap.

We present an atomistic study of the strain field, the one-particle electronic spectrum and the oscillator strength of the fundamental optical transition in chemically disordered InxGa1−xAs pyramidal quantum dots (QDs). Interdiffusion across the interfaces of an originally "pure" InAs dot buried in a GaAs matrix is simulated through a simple model, leading to atomic configurations where the abrupt hetero-interfaces are replaced by a spatially inhomogeneous composition profile x. Structural relaxation and the strain field calculations are performed through the Keating valence force field (VFF) model, while the electronic and optical properties are determined within the empirical tight-binding (ETB) approach. We analyze the relative impact of two different aspects of the chemical disorder, namely: (i) the effect of the strain relief inside the QD, and (ii) the purely chemical effect due to the group-III atomic species interdiffusion. We find that these effects may be quantitatively comparable, significantly affecting the electronic and optical properties of the dot. Our results are discussed in comparison with recent luminescence studies of intermixed QDs.