Band gap modulation of ZnTe1-xOx alloy film by control of oxygen gas flow rate during reactive magnetron sputtering

Abstract

The band gap energy of ZnTe1-xOx alloy films grown on c-plane sapphire substrates was modulated by controlling the argon-oxygen ratio during radio frequency magnetron sputtering. The ZnTe1-xOx samples were deposited at a substrate temperature of 200 degrees C and with gas mixtures of 2%-8% oxygen in argon. The optical transparency of the ZnTe1-xOx samples was measured in the 1.5-6.0 eV energy range by optical transmission spectra. The optical band gap, obtained from plots of (alpha h nu)(2) as a function of h nu, increased from 2.2 to 4.9 eV with increasing oxygen ratio, believed to be a result of a change in bonding structure through composition exchange during film deposition by reactive magnetron sputtering. These results show that the band gap energy of ZnTe1-xOx, ZnOTeO, and (ZnO)(1-x)(TeO2)(x) alloy films can be modulated, making them more suited for applications as windows and as active layers for ZnTe-based intermediate band solar cells.