Defect properties andp-type doping efficiency in phosphorus-doped ZnO

Abstract

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 ${\mathrm{P}}_{\mathrm{Zn}}\ensuremath{-}2{V}_{\mathrm{Zn}}$ 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 ${\mathrm{P}}_{\mathrm{Zn}}\ensuremath{-}2{V}_{\mathrm{Zn}}$ complex is energetically more favorable and becomes the dominant acceptor under O-rich growth conditions.