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.
Bibliographical noteFunding Information:
This paper was supported primarily by the US Department of Energy through the University of Minnesota (UMN) Center for Quantum Materials under DE-SC-0016371. Electron microscopy work by H.Y., J.S.J., and K.A.M was supported by the National Science Foundation (NSF) through the UMN Materials Research Science and Engineering Center (MRSEC) under DMR-1420013 and DMR-2011401. H.Y. also acknowledges a fellowship from the Samsung Scholarship Foundation, Republic of Korea. Parts of this paper were performed in the Characterization Facility, UMN, which receives partial support from NSF through the MRSEC program.
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