Eur. Phys. J. B 78, 497-507 (2010)
https://doi.org/10.1140/epjb/e2010-10761-0

Multiband tight-binding theory of disordered A_xB_1-xC semiconductor quantum dots

Application to the optical properties of alloyed Cd_xZn_1-xSe nanocrystals

Institute for Theoretical Physics, University of Bremen, 28359 Bremen, Germany

Corresponding author: ^a dmourad@itp.uni-bremen.de

Received: 6 October 2010
Revised: 28 October 2010
Published online: 10 December 2010

Abstract

Zero-dimensional nanocrystals, as obtained by chemical synthesis, offer a broad range of applications, as their spectrum and thus their excitation gap can be tailored by variation of their size. Additionally, nanocrystals of the type A_xB_1-xC can be realized by alloying of two pure compound semiconductor materials AC and BC, which allows for a continuous tuning of their absorption and emission spectrum with the concentration x. We use the single-particle energies and wave functions calculated from a multiband sp³ empirical tight-binding model in combination with the configuration interaction scheme to calculate the optical properties of Cd_xZn_1-xSe nanocrystals with a spherical shape. In contrast to common mean-field approaches like the virtual crystal approximation (VCA), we treat the disorder on a microscopic level by taking into account a finite number of realizations for each size and concentration. We then compare the results for the optical properties with recent experimental data and calculate the optical bowing coefficient for further sizes.