Oxygen-vacancy-assisted recovery process for increasing electron mobility in n-type BaSnO3 epitaxial thin lms

Abstract

New transparent oxide semiconductors (TOSs) have received extensive interests and demands for the application of current optoelectronic devices. In particular, La-doped BaSnO3 (LBSO) have recently attracted much attention due to the excellent room-temperature (RT) electron mobility ( 320 cm2V􀀀1s􀀀1 at n = 8.0 1019 cm􀀀3 in a single crystal) and the excellent thermal stability [1]. Despite the great potential of LBSO for transparent electronics, epitaxial LBSO lms were reported to show much lower electron mobility than single crystals, which has been ascribed into the high density of line defects, i.e., dislocations, which are generated by lattice mismatch between substrate and lm [2]. In this research, we demonstrate the signicant increase in the room-temperature electron mobility of LBSO by delicately modulating the oxygen vacancy (VO) concentration by post-growth treatment. Through the accurate adjustment of oxygen partial pressure (pO2) under annealing, the roomtemperature mobility of LBSO lms on STO substrates could increase up to 115 cm2V􀀀1s􀀀1 at a carrier concentration of 1.2 1020 cm􀀀3, which results in simultaneous increase of carrier density and mobility [3]. The electrical, optical and structural eects of VO formed during annealing were systematically investigated, and especially, signicant reduction of threading dislocations was directly observed by bright-eld and dark-eld image of transmission electron microscopy and reciprocal space mapping of x-ray diraction. Thus, the enhancement of RT electron mobility by adjusting pO2 was attributed to the annihilation of threading dislocation by high-temperature recovery process, i.e., the dislocation annihilation through oxygen-vacancy-induced climb. Our nding suggests that the interaction between point defects and line defects can be exploited to boost carrier density and mobility in transparent oxide semiconductors.