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

TL;DR

This study demonstrates that high-mobility La-doped BaSnO3 films can be fabricated without buffer layers by using highly oxidative ozone atmospheres, significantly improving electron mobility.

Contribution

It introduces a buffer layer-less fabrication method for LBSO films using ozone atmospheres to enhance mobility, simplifying the process and achieving high performance.

Findings

Achieved electron mobility up to 115 cm2 V-1 s-1 in LBSO films.

Ozone atmospheres relaxed lattice mismatch and reduced Sn2+ states.

Mobility comparable to buffer-layer methods without additional steps.

Abstract

Transparent oxide semiconductors (TOSs) showing both high visible transparency and high electron mobility have attracted great attention towards the realization of advanced optoelectronic devices. La-doped BaSnO3 (LBSO) is one of the most promising TOSs because its single crystal exhibits a high electron mobility. However, in the LBSO films, it is very hard to obtain high mobility due to the threading dislocations, which are originated from the lattice mismatch between the film and the substrate. Therefore, many researchers have tried to improve the mobility by inserting a buffer layer. While the buffer layers increased 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 single crystal values. We show herein that the electron mobility of LBSO films can be improved without inserting any buffer layers if the films are grown under highly oxidative ozone (O3) atmospheres. The O3 environments relaxed the LBSO lattice and reduced the formation of Sn2+ states, which are known to suppress the electron mobility in LBSO. The resultant O3-LBSO films showed improved mobility values up to 115 cm2 V-1 s-1, which is among the highest in LBSO films on SrTiO3 substrates and comparable to LBSO films with buffer layers.