Electronic structure and band gap composition-dependence of the II-VI quaternary alloys

TL;DR

This paper develops a tight-binding model to accurately predict the band gap variation in II-VI quaternary alloys, extending previous models for ternary alloys and matching recent experimental data.

Contribution

It introduces a generalized virtual crystal approximation-based Hamiltonian for quaternary alloys, improving band gap prediction accuracy.

Findings

The model reproduces experimental band gap changes with alloy composition.

It successfully extends ternary alloy descriptions to quaternary systems.

The approach offers a straightforward way to analyze complex alloy systems.

Abstract

Based on a successful description of II-VI ternary alloys, which introduces an empirical bowing parameter to the widely used virtual crystal approximation, we set up a tight-binding Hamiltonian to describe the Zn_{1-y}Cd_ySe_{1-x}Te_x and Zn_{.9}Cd_{.1}S_{.07}Se_{.93} quaternary alloys. We just use a formula that can be thought as a straightforward generalization of the virtual crystal approximation for this case. Our Hamiltonians reproduce very well the change in the band gap value with the composition observed in recent experimental reports.