Structure-property relationships and mobility optimization in sputtered La-doped BaSn O3 films: Toward 100 c m2 V-1 s-1 mobility

The wide band gap semiconducting perovskite BaSnO3 is of high current interest due to outstanding room temperature mobility at high electron density, fueled by potential applications in oxide, transparent, and power electronics. Due in part to a lack of lattice-matched substrates, BaSnO3 thin films suffer from high defect densities, however, limiting electron mobility. Additionally, the vast majority of BaSnO3 thin film research has focused on pulsed laser deposition or molecular beam epitaxy. Here, we present an exhaustive optimization of the mobility of Ba0.98La0.02SnO3 films grown by a scalable, high-throughput method: high-pressure-oxygen sputter deposition. Considering target synthesis conditions, substrate selection, buffer layer structure, deposition temperature, deposition rate, thickness, and postdeposition annealing conditions, and by combining high-resolution x-ray diffraction, reciprocal space mapping, rocking curve analysis, scanning transmission electron microscopy, atomic force microscopy, and temperature-dependent electronic transport measurements, detailed understanding of synthesis-structure-property relationships is attained. Optimized room temperature mobility of 96cm2V-1s-1 is achieved in vacuum-annealed GdScO3(110)/BaSnO3(120 nm)/Ba0.98La0.02SnO3(200 nm) heterostructures, as well as 92cm2V-1s-1 on unbuffered substrates and 87cm2V-1s-1 without postdeposition annealing. These results, including important trends in defect densities and a surprising dependence of mobility on lattice mismatch, substantially expand the understanding of the interplay between deposition conditions, microstructure, and transport in doped BaSnO3 films, establishing competitive mobilities in films fabricated via a scalable, high-throughput, industry-standard technique.