Abstract
We present the electronic transport properties of BaZrS3 thin films grown epitaxially by gas-source molecular beam epitaxy. We observe n-type behavior in all samples, with carrier concentration ranging from 4 x 1018 to 4 x 1020 cm-3 at room temperature (RT). We observe a champion RT Hall mobility of 11.1 cm2 V−1 s−1, which is competitive with established thin-film photovoltaic absorbers. Temperature-dependent Hall mobility data show that phonon scattering dominates at room temperature, in agreement with computational predictions. X-ray diffraction data illustrate a correlation between mobility and antiphase boundary concentration, illustrating how microstructure can affect transport. Despite the well-established environmental stability of chalcogenide perovskites, we observe significant changes to electronic properties as a function of storage time in ambient conditions. With the help of secondary ion mass spectrometry measurements, we propose and support a defect mechanism that explains this behavior: as-grown films have a high concentration of sulfur vacancies that are shallow donors (V's or V"s), which are converted into neutral oxygen defects (Oxs) upon air exposure. We discuss the relevance of this defect mechanism within the larger context of chalcogenide perovskite research, and we identify means to stabilize the electronic properties.
