A theoretical study of thermal stability and electronic properties of wurtzite and zincblende ZnOxS1-x

A theoretical study on the thermodynamic stability and electronic properties of wurtzite (WZ) and zincblende (ZB) ZnOxS1-x as been carried out with first-principles methods. Special quasi-random structures (SQSs) are employed to model the random alloys and from the calculated phase diagram, it is clear that the solubility limits in the mother lattices (sulfur-doped WZ-ZnO and oxygen-doped ZB-ZnS) are very small for both WZ and ZB phases. Detailed electronic and structural properties of quasi-ordered structures were investigated by examining alloy configurations in different supercells. In particular, we found that the concentration dependence of the band gap is highly nonlinear and the large bowing coefficients are also sensitive to the composition. The intriguing difference in band gaps and bowing coefficient between WZ- and ZB-ZnO1-xSx is evident. This result from first-principles calculations predicts that the band gap bowing with the WZ structure can be quite different from that with the ZB structure in some semiconductor alloys and deserves further experimental investigation for verification.