Electromechanical field effects in InAs/GaAs quantum dots based on continuum k→·p→ and atomistic tight-binding methods

Abstract A comparison between k → · p → and tight-binding methods for the analysis of InAs/GaAs quantum dot bandstructures is presented based on a fully coupled computation of electromechanical effects. Electromechanical effects are addressed using a continuum elastic model for the k → · p → method and a pre-conditioned Valence Force Field algorithm for the tight-binding atomistic calculations. The Valence Force Field method allows the direct identification of the impact of internal strain. Results to ensure model parameter consistency between the two methods are also given by comparing bulk and unstrained quantum-well dispersion relations. The quantum dot size dependence of the bandstructure is investigated based on the models including electromechanical fields. Additionally, the effect of the electromechanical fields is studied for a specific dot size by comparing results with and without electromechanical fields. Good agreement is found for the confined energy levels but model differences show up in the symmetry of probability densities mainly due to the underlying crystal structure details taken into account by the tight-binding method but lacking in the k → · p → formalism. The latter follows from not including bulk inversion-asymmetry effects in the k → · p → method. Inclusion of piezoelectric field effects in the k → · p → method, however, restores the correct symmetry in the k → · p → model (in agreement with the tight-binding symmetry). Results are also given for oscillator strengths where both quantitative and qualitative differences are found in the comparison of k → · p → and tight-binding models.