First-principles study of Sn and Ca doping in $\mathrm{Cu}\mathrm{In}{\mathrm{O}}_2$

The roles of Ca and Sn doping for $p$- and $n$-type $\mathrm{Cu}\mathrm{In}{\mathrm{O}}_2$ were studied from first principles DFT calculations, which may lead to a better understanding of the dopant effects and further help to speed up the progress of new doping techniques. Currently Ca and Sn dopants are widely used in $\mathrm{Cu}\mathrm{In}{\mathrm{O}}_2$ experiments, but the reported carrier concentrations were still too low to support practical device design. In this theoretical approach, we demonstrated that Ca is a deep acceptor and Sn is a deep donor which are unlikely to account for the enhanced electrical conductivity in experiments. We further propose that amorphous ${\mathrm{In}}_2{\mathrm{O}}_3$ may be partially responsible for the difference between the experiment and modeling.

Figure 1

Formation energy of Ca or Sn dopant substituting Cu or In, as a function of $E_F$ in (a) oxygen rich and (b) oxygen poor conditions. Charge state $q$ determines the slope of each line segment. Solid dots denote values of $E_F$ where transition between charge states occurs.

Figure 2

Formation energy of intrinsic defects of donor-like (a), (b) and acceptor-like (c), (d) as a function of oxygen chemical potential when $E_F$ is at the CBM (a), (c) or the VBM (b), (d).