Mobility-Electron Density Relation Probed via controlled Oxygen Vacancy Doping in Epitaxial BaSnO$_{\mathrm{\mathbf{3}}}$

The recently discovered high 300 K mobility in wide band gap semiconducting BaSnO$_{\mathrm{3}}$ is of exceptional interest for perovskite oxide heterostructures. Critical issues in epitaxial films include determination of the optimal dopant, and understanding the mobility-electron density ($\mu $-$n)$ relation. These are addressed here through a transport study of BaSnO$_{\mathrm{3}}$ films with oxygen vacancy doping controlled \textit{via} reduction temperature. Single-phase, close-to-stoichiometric, smooth, epitaxial films were grown \textit{via} high pressure oxygen sputter deposition. $n$ at 300 K can be tuned from 5$\times$ 10$^{\mathrm{19}}$ cm$^{\mathrm{-3}}$ to as low as 2$\times$ 10$^{\mathrm{17}}$ cm$^{\mathrm{-3}}$, which drives a weak- to strong-localization transition accompanied by a 10$^{\mathrm{4}}$-fold increase in resistivity. This reveals $\mu \quad \propto $ $n^{\mathrm{0.65}}$ over the entire $n$ range probed, important for understanding mobility-limiting scattering mechanisms. La-doping has also been explored with this growth method; results at high electron density will be discussed, with a view to mobility optimization. Work supported by the NSF MRSEC under DMR-1420013.