Buffer layer-less fabrication of a high-mobility transparent oxide semiconductor, La-doped BaSnO3

Abstract

La-Doped BaSnO₃ (LBSO) is one of the most promising transparent oxide semiconductors because its single crystal exhibits high electron mobility; therefore, it has drawn significant attention in recent years. However, in the LBSO films, it is very hard to obtain high mobility due to threading dislocations, which are caused by the lattice mismatch between the film and the substrate. While previous studies have reported that insertion of buffer layers increases the electron mobilities; this approach leaves much to be desired since it involves a two-step film fabrication process, and the enhanced mobility values are still significantly lower than the single crystal values. Thus, herein, we show that the electron mobility of the LBSO films can be improved without the insertion of any buffer layers if the films are grown under highly oxidative ozone (O₃) atmospheres. The O₃ environment relaxes the LBSO lattice and reduces the formation of the Sn²⁺ states, which are known to suppress the electron mobility in LBSO. The resultant O₃-LBSO films show improved mobility values up to 115 cm² V⁻¹ s⁻¹, which are among the highest values reported for the LBSO films on SrTiO₃ substrates and comparable to those of the LBSO films with buffer layers.