Resonant Ta Doping for Enhanced Mobility in Transparent Conducting SnO ₂

Abstract

Transparent conducting oxides (TCOs) are ubiquitous in modern consumer electronics. SnO₂ is an earth abundant, cheaper alternative to In₂O₃ as a TCO. However, its performance in terms of mobilities and conductivities lags behind that of In₂O₃. On the basis of the recent discovery of mobility and conductivity enhancements in In₂O₃ from resonant dopants, we use a combination of state-of-the-art hybrid density functional theory calculations, high resolution photoelectron spectroscopy, and semiconductor statistics modeling to understand what is the optimal dopant to maximize performance of SnO₂-based TCOs. We demonstrate that Ta is the optimal dopant for high performance SnO₂, as it is a resonant dopant which is readily incorporated into SnO₂ with the Ta 5d states sitting ∼1.4 eV above the conduction band minimum. Experimentally, the band edge electron effective mass of Ta doped SnO₂ was shown to be 0.23<i>m</i> ₀, compared to 0.29<i>m</i> ₀ seen with conventional Sb doping, explaining its ability to yield higher mobilities and conductivities.