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 ${\mathrm{P}}_2{\mathrm{O}}_5$ and ${\mathrm{Zn}}_3{\mathrm{P}}_2$. 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, ${\mathrm{P}}_{\mathrm{O}}$ acceptors are compensated by dominant donors such as ${\mathrm{P}}_{\mathrm{Zn}}$, leading to $n$-type conduction. Although a ${\mathrm{P}}_{\mathrm{Zn}}-2V_{\mathrm{Zn}}$ 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 ${\mathrm{P}}_2{\mathrm{O}}_5$. On the other hand, when ${\mathrm{Zn}}_3{\mathrm{P}}_2$ is used as the P dopant source, the ${\mathrm{P}}_{\mathrm{Zn}}-2V_{\mathrm{Zn}}$ complex is energetically more favorable and becomes the dominant acceptor under O-rich growth conditions.

• Received 5 July 2005

DOI:https://doi.org/10.1103/PhysRevB.73.024117