A Theoretical Study of the Heavy and Light Hole Properties of Cd1-xZnxS Quantum Dot Superlattices

Saber Marzougui

doi:10.11648/j.ijmsa.20140305.30

Abstract

This work reports on a theoretical investigation of superlattices based on Cd1-xZnxS quantum dots embedded in an insulating material. This system, considered as a series of flattened cylindrical quantum dots with a finite barrier at the boundary, is studied using the tight binding approximation. The ground miniband width and the longitudinal effective mass, in the case of the heavy and light holes, have been computed as a function of zinc composition for different inter-quantum dot separations. An analysis of the results shows that the Zn composition x = 0.8 are appropriate to give rise a superlattice behavior for the light holes. As for the heavy holes, it has been showed the strong localization character of theses carriers in the Cd1-xZnxS nanostructures.

Highlights

In the last decades, films of Cd1−xZnxS have found wide applications in electrical, optical and electro – optical devices [1,2,3].The high potentialities of these films is mainly due to their utility as window materials in heterojunction solar cells with a p-type absorber like CuInSe2, CuInxGa1-xSe2 or CuSnSz Se1-z [4,5,6]
In a second step, the coupling in the case of superlattices based on Cd1-xZnxS quantum dots embedded in an insulating material with use of several potential models and different methods (Kronig – Penney method, sinusoidal and triangular potentials, Tight Binding approximation...) [2429]
For the heavy and light holes, the longitudinal dispersion relation of the Γ1 − miniband, given by Eq (3), as a function of the ZnS molar fraction, for superlattice periods going from d = 1.5 nm to d= 2.5 nm

Summary

Introduction

Films of Cd1−xZnxS have found wide applications in electrical, optical and electro – optical devices [1,2,3].The high potentialities of these films is mainly due to their utility as window materials in heterojunction solar cells with a p-type absorber like CuInSe2, CuInxGa1-xSe2 or CuSnSz Se1-z [4,5,6]. By restricting the study to the ground state for both electrons and holes, we have calculated, in a first step, the shape of the confinement potentials, the quantized energies, their related envelope wave – functions and the QDs sizes [21]. In a second step, for electrons and holes, the excited bound states [22]. All these calculations have been made versus the zinc composition

Objectives

Results

Conclusion