Band gap bowing of binary alloys: Experimental results compared to theoretical tight-binding supercell calculations for CdZnSe

TL;DR

This paper combines experimental measurements with tight-binding supercell calculations to analyze the band gap bowing in CdZnSe alloys, providing insights into how alloy composition affects electronic properties.

Contribution

It introduces a detailed tight-binding supercell model for binary alloys and compares its predictions with experimental data for CdZnSe.

Findings

Good agreement between theory and experiment on band gap bowing

Optimal supercell size and basis set identified for accurate modeling

Experimental data from MBE and PL measurements support theoretical results

Abstract

Compound semiconductor alloys of the type ABC find widespread applications as their electronic bulk band gap varies continuously with x, and therefore a tayloring of the energy gap is possible by variation of the concentration. We model the electronic properties of such semiconductor alloys by a multiband tight-binding model on a finite ensemble of supercells and determine the band gap of the alloy. This treatment allows for an intrinsic reproduction of band bowing effects as a function of the concentration x and is exact in the alloy-induced disorder. In the present paper, we concentrate on bulk CdZnSe as a well-defined model system and give a careful analysis on the proper choice of the basis set and supercell size, as well as on the necessary number of realizations. The results are compared to experimental results obtained from ellipsometric measurements of CdZnSe layers prepared by molecular beam epitaxy (MBE) and photoluminescence (PL) measurements on catalytically grown CdZnSe nanowires reported in the literature.