On the bowing parameter in Cd1-xZnxTe

Cd1-xZnxTe thin films were prepared on 7059 Corning glass substrates using an rf magnetron sputtering system and CdTe(1-y)+ZnTe(y) targets. The concentration (x) of Zn in the films did not coincide with the relative weight (y) of the ZnTe powder in the compressed targets. Values of x were in the range 0-0.30 as determined from x-ray diffraction patterns. The band gap energy (E-g) of the Cd1-xZnxTe samples was calculated from the photoreflectance spectra measured on the films. The position of the experimental points in the E-g versus x plot show a deviation from the phenomenological quadratic relation E-g=E-g0+ax+bx(2) calculated within the virtual crystal approximation (VCA). The depart of the E-g values for higher Zn concentrations from the expected VCA model is probably due to a larger clustering of Zn atoms and/or a percolation phenomena. We obtain fitted values for the parameters a and b within the VCA approach. Comparison with data reported by other authors is made. (C) 2004 American Institute of Physics.