Band gap energy in Zn-rich $\pmb{Zn_{1-x}Cd_xTe}$ thin films grown by r.f. sputtering

Abstract

Ternary $Zn_{1-x}Cd_{x}Te$ semiconducting thin films were grown on 7059 Corning glass substrates at room temperature by co-sputtering from a ZnTe-Cd target. The visible Cd-area onto ZnTe target was varied to cover 0% - 4% of the total area. The optical and structural properties of the films were analysed as a function of the Cd concentration ($x$) on the layers. The sharp diffraction lines indicate mainly the ZnTe in cubic phase. When the cadmium was incorporated into the ZnTe lattice, the band gap energy $(E_g)$ decreased from 2.2748 eV ($x$=0) to 2.2226 eV ($x$= 0.081). We found a linear relationship between $E_g$ and ($x$) in the interval of ($x$) studied, that predicts a value of the bowing parameter b in the $E_g(x) = E_{go} + ax + bx^{2}$ relationship, which coincides with the value of b calculated by making the same study for Cd-rich CdZnTe. This result becomes interesting given the large number of values reported for b and $a$ for $E_g$($x$) of this ternary material.