Influence of symmetry and Coulomb correlation effects on the optical properties of nitride quantum dots

Abstract

The electronic and optical properties of self-assembled InN/GaN quantum dots (QDs) are investigated by means of a tight-binding model combined with configuration interaction calculations. Tight-binding single particle wave functions are used as a basis for computing Coulomb and dipole matrix elements. Within this framework, we analyze multi-exciton emission spectra for two different sizes of a lens-shaped InN/GaN QD with wurtzite crystal structure. The impact of the symmetry of the involved electron and hole one-particle states on the optical spectra is discussed in detail. Furthermore we show how the characteristic features of the spectra can be interpreted using a simplified Hamiltonian which provides analytical results for the interacting multi-exciton complexes. We predict a vanishing exciton and biexciton ground state emission for small lens-shaped InN/GaN QDs. For larger systems we report a bright ground state emission but with drastically reduced oscillator strengths caused by the quantum confined Stark effect.

Direct generation of linearly polarized single photons with a deterministic axis in quantum dots

“…Consequently, the calculations show that in a-plane InGaN QDs, the DOLP ρ is very insensitive against shape anisotropies and indium composition changes. It should be noted that, in principle, Coulomb effects can mix contributions from excited (single-particle) states into the excitonic ground state [46]. However, our calculations reveal that the first few excited hole states are all almost entirely | -Y 〉 like in character.…”

Tight‐binding model for the electronic and optical properties of nitride‐based quantum dots

“…In accordance with the CI calculations, the lower energy line is dominated by contributions where the electron is excited in the s-shell and the hole in the p-shell, whereas the higher energy line corresponds mainly to the excitation of the hole in the s-shell and the electron in the p-shell. This is in accordance with the dipole selection rules, which have also been validated by a group theoretical analysis [42]. The influence of the built-in field in the structure redshifts the whole excitonic spectrum by about 220 meV.…”

“…As discussed in detail in Ref. [42], the degeneracy in the absence of the spin-orbit coupling is related to the C 3v symmetry of the combined system of underlying crystal structure and QD geometry. A splitting, albeit quite small, of these states is introduced by the inclusion of the spin-orbit coupling, since in this case one has to deal with the double group C 3v .…”

Single quantum dot nanolaser

“…These input entities can be determined on various levels of refinement. Atomistic tight-binding calculations have been used to determine confinement energies, wave functions and interaction matrix elements for QD systems [185,186]. As an alternative to this computationally expensive approach, that represents a research field on its own, frequently continuum methods based on effective mass models [187] or k¡p-Hamiltonians [188][189][190] have been applied.…”