Electronic and Optical Properties of Quantum Dots: A Tight-Binding Approach

Semiconductor quantum dots (QDs) are of great topical interest due to the possibility to study basic quantum phenomena and their potential for novel applications. Here, the electronic and optical properties of semiconductor QDs are studied by means of tight-binding (TB) models combined with configuration interaction calculations. An empirical TB model is used to investigate the electronic states of group II-VI semiconductor QDs with a zinc blende structure. Within this approach pyramidal-shaped CdSe QDs embedded in a ZnSe matrix as well as spherical CdSe nanocrystals are studied. The theoretical results are found to be in excellent agreement with recent experimental data. Additionally, we study the electronic and optical properties of self-assembled nitride QDs. Excitonic absorption as well as multi-exciton emission spectra are analyzed for a series of different lens-shaped InN/GaN QDs. A dark exciton and biexciton ground state for small QDs is found. For larger structures, the strong electrostatic built-in fields lead to a level reordering for the hole states, which results in a bright exciton ground state. Furthermore, truncated pyramidal GaN/AlN QDs with zinc blende structure are investigated. Again, Coulomb and dipole matrix elements are evaluated from the single-particle wave functions and the optical spectra are analyzed. Finally, the results of our atomistic TB description are compared with continuum-like approaches.