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Optical Fine Structure of II-VI and III-V Nanocrystals: The Role of d Orbitals in a Tight-Binding Approach
Published
Author(s)
J G. Diaz, Garnett W. Bryant, W Jaskolski
Abstract
The electronic structure of GaAs and CdSe nanocrystals is studied by using a nearest-neighbor tight-binding model extended to include d orbitals. Our results show that the inclusion of $d$ orbitals in a minimal basis set is necessary for a proper description of the lowest electron states, especially in the strong confinement regime. We have checked that simpler sp3s* models yield an incorrect description of electron states made from bulk band-states away from the Brillouin zone center. For GaAs nanocrystals with sizes below 2.5 nm, the d model predicts that the ground electron state is primarily built of L-point band-states, giving the nanocrystal an indirect-gap character. The sp3d5 model also explains successfully the evolution of the absorption peaks in CdSenanocrystals with confinement. We provide an interpretation of the fine band-edge structure based on an orbital-forbidden dark exciton mechanism, which is in agreement, for the first time, with both the resonant and
Diaz, J.
, Bryant, G.
and Jaskolski, W.
(2021),
Optical Fine Structure of II-VI and III-V Nanocrystals: The Role of d Orbitals in a Tight-Binding Approach, Physica Status Solidi
(Accessed February 6, 2025)