Doping by Large-Size-Mismatched Impurities: The Microscopic Origin of Arsenic- or Antimony-Dopedp-Type Zinc Oxide

Based on first-principles calculations, a model for large-size-mismatched group-V dopants in ZnO is proposed. The dopants do not occupy the O sites as is widely perceived, but rather the Zn sites: each forms a complex with two spontaneously induced Zn vacancies in a process that involves fivefold As coordination. Moreover, an ${\mathrm{As}}_{\mathrm{Zn}}\mathrm{\text{−}}2V_{\mathrm{Zn}}$ complex may have lower formation energy than any of the parent defects. Our model agrees with the recent observations that both As and Sb have low acceptor-ionization energies and that to obtain $p$-type ZnO requires O-rich growth or annealing conditions.