Resonant Ta Doping for Enhanced Mobility in Transparent Conducting SnO2
<div>Transparent conducting oxides (TCOs) are ubiquitous in modern consumer electronics. SnO<sub>2</sub> is an earth abundant, cheaper alternative to In<sub>2</sub>O<sub>3</sub> as a TCO however, its performance in terms of electrical properties lags behind that of In<sub>2</sub>O<sub>3</sub>. Based on the recent discovery of mobility and conductivity enhancements in In<sub>2</sub>O<sub>3</sub> from resonant dopants, we use a combination of state-of-the-art hybrid density functional theory calculations, high resolution photoelectron spectroscopy and semiconductor statistics modelling to understand what the optimal dopant is to maximise performance of SnO<sub>2</sub>-based TCOs. We demonstrate that Ta is the optimal dopant for high performance SnO<sub>2</sub>, as it is a resonant dopant which is readily incorporated into SnO<sub>2</sub> with the Ta 5d states sitting ~1.4 eV above the conduction band minimum. Experimentally, the electron effective mass of Ta doped SnO<sub>2</sub> was shown to be 0.23m<sub>0</sub>, compared to 0.29m<sub>0</sub> seen with conventional Sb doping, explaining its ability to yield higher mobilities and conductivities.</div><div><br></div>