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

TL;DR

This study reveals that the carrier mobility in La-doped BaSnO3 thin films significantly depends on film thickness, reaching saturation at a certain point regardless of lattice mismatch or surface morphology differences.

Contribution

It demonstrates the dominant influence of film thickness on carrier mobility in La-doped BaSnO3, providing insights for optimizing its electronic properties.

Findings

Mobility increases with film thickness and saturates at ~100 cm2 V-1 s-1.

Mobility behavior is independent of lattice mismatch and surface morphology.

Carrier concentration approaches the nominal doping level as mobility saturates.

Abstract

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.