Electronic properties of Ag-doped ZnO: DFT hybrid functional study

Studying the possibility of a p-type conduction mechanism in the Ag-doped ZnO can clarify persisting ambiguities in the related materials and devices. Here, utilizing the first principles study by hybrid functional calculations, we conclude that the potential acceptor defects Ag-Zn and V-Zn are rare in the low Fermi level conditions required for p-type conduction and, hence, can hardly contribute to the hole generation in ZnO regardless of the assumed O-rich condition. Our results also reveal the exothermicity of the reaction between V-O and Ag-Zn to form the complex defect V-O-2Ag(Zn) which is shown to be a less effective donor than V-O. The conversion of the V-O to a less electronically effective complex defect is proposed as the mechanism responsible for the conductivity instabilities in the silver doped zinc oxide.