Electronic structures of [110]-faceted self-assembled pyramidal InAs/GaAs quantum dots

We calculate the electronic structures of pyramidal quantum dots with supercells containing 250000 atoms. using spin-orbit-coupled, nonlocal, empirical pseudopotentials. We compare the results with previous theoretical calculations, Our calculation circumvents the approximations underlying the conventional effective-mass approach: we describe the potential, the strain and the wave functions using atomistic rather than continuum models. The potential is given by a superposition of screened atomic pseudopotentials, the strain is obtained from minimizing the atomistic strain energy, and the wave function is expanded using a plane-wave basis set. We find the following. (1) The conduction bands. are formed essentially from single envelope functions, so they can be classified according td the: nodal structure as s, p, and d. However, due to strong multiband coupling, most notably light hole with heavy hole, the valence states cannot be classified in the language of single-band envelope functions. In fact, the hole states have no nodal planes. (2) There is a strong anisotropy in the polarization of the lowest valence state to conduction state optical transition. This is in contrast to the eight band k.p model, which finds essentially zero anisotropy. (3) There are at least four bound electron states for a 113-Angstrom-based quantum dot, This number of bound states is larger than that found in eight band kp calculations. (4) Since our atomistic description retains the correct C-2v symmetry of a square-based pyramid made of zinc-blende solids, we find that the otherwise degenerate p states are split by about 25 meV. This splitting is underestimated in the eight-band k.p calculation. [50163-1829(99)00608-6].