First-principles study of Ag-based p-type doping difficulty in ZnO

The first-principles with pseudopotentials method based on the density functional theory was applied to calculate the geometric structure, the formation energy of impurities and the electronic structure of ZnO doped with Ag. The calculated conclusions show that the O-rich condition is better for p-type doping than the Zn-rich condition. The Ag dopant prefers to occupy the substitutional Zn site, which results in a deep acceptor. Furthermore, self-compensation via Ag-i, doping by Ag is almost impossible. It is also found that our results are in good agreement with other calculated and experimental results. (C) 2007 Elsevier B.V. All rights reserved.