2009 Volume 50 Issue 5 Pages 1067-1070
Solid solutions of Zn1−xCdxO and Zn1−xMgxO (0≤x≤1) with wurtzite structures are systematically investigated by first principles calculations with special interests on the dependence of energetics and electronic structures on the alloy structure. Alloying ZnO with CdO shows a linear increase in the lattice parameters when we choose energetically favorable alloy structures. On the other hand, they do not show such a linear trend when alloyed with MgO. Formation energy with reference to the end-member oxides of wurtzite structures is positive for Zn1−xCdxO alloys, whereas it is slightly negative for Zn1−xMgxO alloy. They are consistent with the experimental fact that highly concentrated solid solutions are easier to be formed in Zn1−xMgxO alloys. The band gap shows a monotonous decrease in Zn1−xCdxO and increase in Zn1−xMgxO with the solute concentration. In Zn1−xCdxO, Cd has an orbital component as large as that of Zn at the bottom of the conduction band. On the other hand, the contribution of Mg is much smaller in Zn1−xMgxO. They are consistent with the changes in the band gap with the composition.