First-principles study of electronic and optical properties in wurtzite Zn_{1-x}Cd_xO

TL;DR

This study uses first-principles calculations to analyze how increasing Cd content in wurtzite ZnO affects its electronic structure and optical properties, revealing a decrease in band gap and shifts in optical transition energies.

Contribution

It provides detailed first-principles insights into the electronic and optical property changes in Zn1-xCdxO with varying Cd concentrations, including band gap bowing and optical constant variations.

Findings

Optical band gap decreases from 3.2 to 2.84 eV with Cd doping.

Bowing parameter for optical band gap is approximately 1.21 eV.

Optical transition energies shift to lower energies as Cd content increases.

Abstract

A first-principles study has been performed to evaluate the electronic and optical properties of wurtzite Zn1-xCdxO up to x=0.25. We have employed the Perdew-Burke-Ernzerhof (PBE) form of generalized gradient approximation within the framework of density functional theory (DFT). Calculations have been carried out in different configurations. With the increasing Cd concentrations, the band gap of Zn1-xCdxO is decreased due to the increase of s states in conduction band. The results of imaginary part of dielectric function indicate that the optical transition between O 2p states in the highest valence band and Zn 4s states in the lowest conduction band has shifted to low energy range as the Cd concentrations increase. Besides, the optical band gap decreases from 3.2 to 2.84 eV with increasing Cd concentrations from 0 to 0.25. Meanwhile, the bowing parameter b, which has been obtained by fitting the results of optical band gap, is about 1.21 eV. The optical constants of pure ZnO and Zn0.75Cd0.25O, such as optical conductivity, loss function, refractive index and reflectivity, have been discussed.