Defect properties and p -type doping efficiency in phosphorus-doped ZnO

Based on first-principles pseudopotential calculations, we investigated the electronic structure of various P-related defects in ZnO and the p-type doping efficiency for two forms of P dopant sources such as P₂O₅ and Zn₃P₂. As compared to N dopants, a substitutional P at an O site has a higher ionization energy of about 0.62 eV, which makes it difficult to achieve p-type ZnO. Under Zn-rich growth conditions, PO acceptors are compensated by dominant donors such as PZn, leading to n-type conduction. Although a PZn-2VZn complex, which consists of a substitutional P at a Zn antisite and two Zn vacancies, acts as an acceptor, the formation of Zn vacancies is more probable on going to O-rich conditions for the dopant source using P₂O₅. On the other hand, when Zn₃P₂ is used as the P dopant source, the PZn-2VZn complex is energetically more favorable and becomes the dominant acceptor under O-rich growth conditions.