Optical Fine Structure of II-VI and III-V Nanocrystals: The Role of d Orbitals in a Tight-Binding Approach

Published

October 12, 2021

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

Citation

Physica Status Solidi

Pub Type

Journals

Keywords

electronic structure, nanocrystal, optical properties, quantum dot

Citation

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 April 26, 2024)