Abstract
We calculate the height dependence of recombination energies, polarization, and radiative lifetimes of the optical transitions of various excitonic complexes: neutral excitons , negatively and positively charged trions, and biexcitons in lens-shaped, self-assembled quantum dots. By using an atomistic pseudopotential method combined with the configuration-interaction method, we predict the following. (i) The recombination energy of the lowest transition of blueshifts as height increases, whereas that of redshifts. Remarkably, the recombination of shows a redshift at small heights, reaches a maximum shift, and then blueshifts for taller dots. This feature results from the height dependence and relative magnitude of the interelectronic direct Coulomb interaction. (ii) Changes in dot height lead to a bound-to-unbound crossover for , , and . (iii) When considering the [110] and directions, the lowest transitions of and manifest [110] vs in-plane polarization anisotropy that switches sign as a function of height as well as alloy randomness. and show transitions with negligible polarization anisotropy regardless of height. (iv) The ground state of is split in a low-energy pair that is forbidden (dark) and a high-energy pair that is allowed; thus, at , the radiative lifetime is long due to the dark exciton. On the other hand, at , decreases moderately as height increases and its magnitude ranges from . The ground state of and , and that of is allowed (bright); so, , , and are fast even at . These radiative lifetimes depend weakly on height. In addition, , while . We compare our predictions with available spectroscopic data.
- Received 1 September 2005
DOI:https://doi.org/10.1103/PhysRevB.72.245318
©2005 American Physical Society