Large thickness dependence of the carrier mobility in a transparent oxide semiconductor, La-doped BaSnO3

Abstract

In this study, we report that the carrier mobility of 2%-La-doped BaSnO3 (LBSO) films on (001) SrTiO3 and (001) MgO substrates strongly depends on the thickness, whereas it is unrelated to the film/substrate lattice mismatch (+5.4% for SrTiO3 and −2.3% for MgO). The films exhibited large differences in lattice parameters, lateral grain sizes (∼85 nm for SrTiO3 and ∼20 nm for MgO), surface morphologies, threading dislocation densities, and misfit dislocation densities. However, the mobility dependences on the film thickness in both cases were almost the same, saturating at ∼100 cm2 V−1 s−1, while the charge carrier densities approached the nominal carrier concentration (=[2% La3+]). Our study clearly indicates that the carrier mobility of LBSO films strongly depends on the thickness. These results would be beneficial for understanding the carrier transport properties and fruitful to further enhance the mobility of LBSO films.