Design of shallow acceptors inZnO: First-principles band-structure calculations

Abstract

$p$-type doping is a great challenge for the full utilization of $\mathrm{ZnO}$ as short-wavelength optoelectronic material. Due to a large electronegative characteristic of oxygen, the ionization energy of acceptors in $\mathrm{ZnO}$ is usually too high. By analyzing the defect wave-function character, we propose several approaches to lower the acceptor ionization energy by codoping acceptors with donor or isovalent atoms. Using the first-principles band-structure method, we show that the acceptor transition energies of ${\mathrm{V}}_{\mathrm{Zn}}\text{\ensuremath{-}}{\mathrm{O}}_{\mathrm{O}}$ can be reduced by introducing ${\mathrm{F}}_{\mathrm{O}}$ next to ${\mathrm{V}}_{\mathrm{Zn}}$ to reduce electronic potential, whereas the acceptor transition energy of ${\mathrm{N}}_{\mathrm{O}}\text{\ensuremath{-}}n{\mathrm{Zn}}_{\mathrm{Zn}}$ $(n=1--4)$ can be reduced if we replace Zn by isovalent Mg or Be to reduce the anion and cation kinetic $p\text{\ensuremath{-}}d$ repulsion, as well as the electronic potential.