Tight-Binding Theory of Quantum Dot Arrays: InAs Dots
Javier Aizpurua, G C. Bryant, W Jaskolski
We model the electronic structure and optical properties of coupled self-assembled dots and period dot arrays by use of tight-binding theory. Coupling in dot molecules and dot arrays modifies significantly the level ordering and state symmetries. We show the effect of the coupling on electron and hole states for vertically stacked and 2-dimensional arrays of InAs self-assembled dots embedded in a GaAs matrix. For 1D arrays of vertically stacked dots, the dispersion of the electron bands is a result of the mixing of the dot envelope functions. In contrast, hole bands depend on the atomic character of the hole states, especially between dots. Antisymmetric interdot mixing of low-energy hole states is favored for widely spaced dots. Symmetric mixing is favorable for closely spaced dots. As a consequence, low energy hole bands exhibit anomalous, negative dispersion in arrays of widely spaced dots and normal dispersion for closely spaced dots. Calculated optical dipole transitions for different dot spacings are compared with experimental photoluminescence data. In two-dimensional arrays of dots, coupling is weaker, giving smaller shifts and normal, positive dispersion of holes for all dot spacing.
Physical Review B (Condensed Matter and Materials Physics)