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The nature of the ground optical transition in an (In,Ga)As/GaP quantum dot is thoroughly investigated through a million atoms supercell tight-binding simulation. Precise quantum dot morphology is deduced from previously reported scanning-tunneling-microscopy images. The strain field is calculated with the valence force field method and has a strong influence on the confinement potentials, principally, for the conduction band states. Indeed, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a large tensile strain region, having mainly Xz character. Photoluminescence experiments under hydrostatic pressure strongly support the theoretical conclusions. [ABSTRACT FROM AUTHOR]

An efficient mechanical and electronic axial approximation of the strained 8 × 8 Hamiltonian is proposed for zinc-blende nanostructures with a cylindrical shape on (100) substrates. Vertically stacked InAs/InP columnar quantum dots (CQDs) for polarization insensitive semiconductor optical amplifier (SOA) in telecommunications applications are studied theoretically. Non-radiative Auger processes in InAs/InP quantum dots (QDs) are also investigated. It is shown that a multiband approach is necessary in both cases. [ABSTRACT FROM AUTHOR]

Vertically stacked InAs/InP columnar quantum dots (CQDs) for polarization insensitive semiconductor amplifier in telecommunications applications are studied theoretically. An axial model is used to predict mechanical, electronic, and optical properties of these CQDs. A crossover from a dominant transverse electric (TE) optical ground state absorption to a dominant transverse magnetic (TM) absorption is predicted for a number of layers equal to about 9 in good agreement with the experiment. The weight of the light hole component of the valence band ground state increases as a function of the number of layers. The change of the TE/TM polarization ratio is also associated to a symmetry change of the heavy hole component. A modification of the aspect ratio of the CQD seems to be the most important factor to explain the change of the electronic states configuration as a function of the strain distribution. [ABSTRACT FROM AUTHOR]

A model is proposed to describe the linear and quadratic piezoelectric potentials in quantum nanostructures with axial symmetry. Semianalytical expressions of the charge densities are given to illustrate the symmetry reduction. The results for InAs/InP quantum dots (QDs) are compared to previous full three-dimensional calculation and to the full isotropic elastic model. The model is well adapted to study various effects for QD: the lattice mismatch, the QD materials composition or alloying, and the QD size or shape. Special emphasis is put on variations of the vertical aspect ratio and the role of the wetting layer. [ABSTRACT FROM AUTHOR]