Structure and transport in high pressure oxygen sputter-deposited BaSnO_3-δ

BaSnO₃ has recently been identified as a high mobility wide gap semiconductor with significant potential for room temperature oxide electronics. Here, a detailed study of the high pressure oxygen sputter-deposition, microstructure, morphology, and stoichiometry of epitaxial BaSnO₃ on SrTiO₃(001) and MgO(001) is reported, optimized conditions resulting in single-phase, relaxed, close to stoichiometric films. Most significantly, vacuum annealing is established as a facile route to n-doped BaSnO_3-δ, leading to electron densities above 10¹⁹ cm^-3, 5 mΩ cm resistivities, and room temperature mobility of 20 cm² V^-1 s^-1 in 300-Å-thick films on MgO(001). Mobility limiting factors, and the substantial scope for their improvement, are discussed.