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

The scattering of charge carriers by line defects, i.e., threading dislocations (TDs), severely limits electron mobility in epitaxial semiconductor films grown on dissimilar substrates. The density of TDs needs to be decreased to further enhance electron mobility in lattice-mismatched epitaxial films and heterostructures for application in high-performance electronic devices. Here, we report a strategy for the post-treatment of epitaxial La-doped BaSnO3 (LBSO) films by delicately controlling the oxygen partial pressure p(O2), which achieved a significant increase in the room temperature (RT) electron mobility (μe) to μe = 122 cm2 V−1 s−1 at a carrier concentration of 1.1 × 1020 cm−3. This mobility enhancement is mostly attributed to an oxygen vacancy-assisted recovery process that reduces the density of TDs by accelerating the movement of dislocations in ionic crystals under a p(O2)-controlled treatment despite an increase in the density of charged point defects. Our finding suggests that accurate control of the interactions between point defects and line defects can reduce dominant carrier scattering by charged dislocations in epitaxial oxide semiconductors that have dissimilar substrates. This method provides alternative approaches to achieving perovskite oxide heterostructures that have high RT μe values. Deliberate introduction of point defects in next-generation oxide semiconductors can reduce mismatch-induced line defects that hinder device performance. Lanthanum-doped barium tin oxides (LBSOs) are photosensitive, transparent semiconductors with promising transistor characteristics that mysteriously slow down when grew on foreign insulating substrates. Junwoo Son and colleagues from South Korea’s Pohang University of Science and Technology have restored the conductivity and electron mobility of heteroepitaxial LBSO thin films by placing them in hot ovens containing water-laden hydrogen gas. X-ray data and electronic measurements revealed this approach enabled to remove small amounts of oxygen atoms from the LBSO film, creating vacant sites that interact with a different type of defect, lines of dislocated atoms that interfere with electron movement. The charged nature of the vacancies enabled a small population to facilitate the rearrangement of these line defects, improving crystal quality. The scattering of charge carriers with line defects, i.e., threading dislocations, needs to be decreased to further enhance electron mobility of lattice-mismatched epitaxial films and heterostructures for the application of high-performance electronic devices. Here, we report a strategy to post-treat epitaxial La-doped BaSnO3 films by delicately controlling oxygen partial pressure p(O2), which achieved significant increase in room temperature electron mobility to 122 cm2∙V−1∙s−1. This mobility enhancement is attributed to an oxygen vacancy-assisted recovery process that reduces the density of dislocations by accelerating the movement of dislocations in ionic crystals under p(O2)-controlled treatment, despite an increase in the density of charged point defects.