Collaboration result with Profs. Hyoungjeen Jeen (Pusan National Univ., Korea), Bin Feng, and Yuichi Ikuhara (Univ. Tokyo, Japan) has been published in Applied Physics Letters. This work was supported by Bilateral Joint Research Projects (JSPS) with Korea (NRF), Network Joint Research Center for Materials and Devices, Dynamic Alliance for Open Innovation Bridging Human, Environment, and Materials (Five-Star Alliance), and Grant-in-Aid for Scientific Research on Innovative Areas (2505) Nanoinformatics.

Publication

Anup V. Sanchela*, Mian Wei, Haruki Zensyo, Bin Feng, Joonhyuk Lee, Gowoon Kim, Hyoungjeen Jeen, Yuichi Ikuhara, and Hiromichi Ohta*, “Large thickness dependence of the carrier mobility in a transparent oxide semiconductor, La-doped BaSnO₃”, Appl. Phys. Lett. 112, 232102 (2018). (DOI: 10.1063/1.5033326)

After the discovery of high electron mobility (~320 cm² V⁻¹ s⁻¹) in the La-doped BaSnO₃ single crystal in 2012 by Kim et al., it has been attracted growing attention how to fabricate La-doped BaSnO₃ thin films showing high electron mobility. Although many researchers have already discussed the way i.e. reducing the lattice mismatch between the film and the substrate to increase the mobility, the achievable mobility is still low, due to the lack of fundamental research such as thickness dependence.

We report herein that the carrier mobility of the 2%-La-doped BaSnO₃ (LBSO) films on (001) SrTiO₃ and (001) MgO substrates strongly depends on the thickness whereas it is unrelated to the lattice mismatch (+5.4 % for SrTiO₃, −2.3 % for MgO). Although we observed large differences in the lattice parameters, the lateral grain size (~85 nm for SrTiO₃, ~20 nm for MgO), the surface morphology and the density of misfit dislocations, the mobility increased almost simultaneously with the thickness in both cases and saturated at ~100 cm² V⁻¹ s⁻¹, together with the approaching to the nominal carrier concentration (=[2 % La³⁺]), clearly indicating that the behavior of mobility depends on the film thickness. The present results would be beneficial to understand the behavior of mobility and fruitful to further enhance the mobility of LBSO films.