Published online by Cambridge University Press: 01 February 2011
We have theoretically evaluated the phase stability and electronic structure of a Zn1-xMgxO solid solution. The enthalpies of formation for both the wurtzite and rocksalt phases of Zn1-xMgxO were calculated using a plane-wave pseudopotential method within the density functional formalism. For 0 < x < 0.5, the calculated enthalpies of formation (&[Delta]H) for the wurtzite phases were lower than those for the rocksalt phases. On the other hand, for x > 0.75, the &[Delta]H values for the wurtzite phase were larger than those for the rocksalt phases. This indicates that the wurtzite phase is more stable for a Zn1-xMgxO solid solution with 0 < x < 0.5, while the rocksalt phase is more stable for a solid solution with x > 0.75. The band gaps of a wurtzite Zn1-xMgxO solid solution increase with increasing Mg content. MgO substitution on Zn1-xMgxO largely affects the conduction band leaving the valence band nearly unchanged. The conduction band minimum (CBM) shifted to higher energy with increasing Mg content. These theoretical results qualitatively agree with the experimental results for Zn1-xMgxO thin films fabricated by RF magnetron co-sputtering.