Dopability, Intrinsic Conductivity, and Nonstoichiometry of Transparent Conducting Oxides

Existing defect models for In2O3 and ZnO are inconclusive about the origin of conductivity, nonstoichiometry, and coloration. We apply systematic corrections to first-principles calculated formation energies ΔH, and validate our theoretical defect model against measured defect and carrier densities. We find that (i) intrinsic acceptors ("electron killers") have a high ΔH explaining high n-dopability, (ii) intrinsic donors ("electron producers") have either a high ΔH or deep levels, and do not cause equilibrium-stable conductivity, (iii) the O vacancy VO has a low ΔH leading to O deficiency, and (iv) VO has a metastable shallow state, explaining the paradoxical coexistence of coloration and conductivity.