Electronic properties of multi-quantum dot structures in Cd<Subscript> 1-x</Subscript>Zn<Subscript> x</Subscript>S alloy semiconductors

In this paper, we present a theoretical study of the quantized electronic states in Cd<Subscript>1-x</Subscript>Zn<Subscript>x</Subscript>S quantum dots. The shape of the confining potential, the subband energies and their eigen envelope wave functions are calculated by solving a one-dimensional Schrödinger equation. Electrons and holes are assumed to be confined in dots having a flattened cylindrical geometry with a finite barrier height at the boundary. Optical absorption measurements are used to fit the bandgap edge of the Cd<Subscript>1-x</Subscript>Zn<Subscript>x</Subscript>S nanocrystals. An analysis of the electron band parameters has been made as a function of Zn composition. Two main features were revealed: (i) a multiplicity in Cd<Subscript>1-x</Subscript>Zn<Subscript>x</Subscript>S quantum dots with different crystalline sizes has been found to fit accurately experimental data in the composition range 0 ≤x ≤0.2; (ii) the fit did not, however, show a multiplicity for x higher than 0.4. On the other hand, we have calculated the energy level structure of coupled Cd<Subscript>1-x</Subscript>Zn<Subscript>x</Subscript>S semiconductor quantum dots using the tight-binding approximation. As is found the Zn composition x=0.4 is expected to be the most favorable to give rise a superlattice behavior for the Cd<Subscript>1-x</Subscript>Zn<Subscript>x</Subscript>S quantum dots studied. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2006