Wide bandgap BaSnO3 films with room temperature conductivity exceeding 104 S cm−1

Abstract

Wide bandgap perovskite oxides with high room temperature conductivities and structural compatibility with a diverse family of organic/inorganic perovskite materials are of significant interest as transparent conductors and as active components in power electronics. Such materials must also possess high room temperature mobility to minimize power consumption and to enable high-frequency applications. Here, we report n-type BaSnO3 films grown using hybrid molecular beam epitaxy with room temperature conductivity exceeding 104 S cm−1. Significantly, these films show room temperature mobilities up to 120 cm2 V−1 s−1 even at carrier concentrations above 3 × 1020 cm−3 together with a wide bandgap (3 eV). We examine the mobility-limiting scattering mechanisms by calculating temperature-dependent mobility, and Seebeck coefficient using the Boltzmann transport framework and ab-initio calculations. These results place perovskite oxide semiconductors for the first time on par with the highly successful III–N system, thereby bringing all-transparent, high-power oxide electronics operating at room temperature a step closer to reality.

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

“…The dominant scattering factor changes with N TD , as previously reported in the plot of the temperature dependence of μ e ðT Þ 12,17 : when N TD is high, the contribution of weakly temperature-dependent μ e,TD is dominant over the contribution of μ e,LO and μ e,CI , so the resultant μ e exhibits negligible change with temperature. However, if N TD is low, μ e,TD is negligible compared to μ e, LO and μ e,CI , so the resultant μ e shows a strong temperature dependence due to LO phonon-limited scattering, charged-impurity-limited scattering, or both.…”

“…However, at a high n > 10 20 cm −3 , μ e significantly decreased with increasing n in our case, but the LBSO thin films grown by MBE with controlled cation stoichiometry 17 maintained a relatively high RT μ e in spite of the increase in n and thus achieved a low resistivity <10 −4 Ω cm by minimizing the impurity scattering induced by the cation off-stoichiometry. Therefore, a further improvement in the RT μ e of our H 2 -treated LBSO through the precise control of the residual point defects and line defects as scattering centers is possible.…”

“…1d). Due to competition between chargeddislocation scattering and charged-impurity scattering, the plot of the RT μ e vs. n is bell-shaped 3,9,12,17 . In the asgrown and Ar-treated LBSO films, μ e was maximized at high n (~5 × 10 20 cm −3 ) and then decreased with decreasing n; this relationship demonstrates the strong influence of charged dislocations as charge traps, scattering centers for carriers, or both, and also shows that this influence reduces n and μ e simultaneously.…”

“…In contrast, the temperature dependence of μ e was affected by the p(O 2 ) used during post-treatment (Fig. 1c) To understand the significant increase in μ e after the H 2 treatment, the resulting μ e can be expressed according to Matthiessen's rule 3,12,17 :…”

“…This low μ e has been attributed to the abundance of TDs 9 that inevitably form during epitaxial growth due to large lattice mismatch with the substrate, e.g., SrTiO 3 or MgO. Therefore, considerable effort has been devoted to decreasing the density of TDs by using substrates with a lattice constant that is similar to or even the same as that of BSO [13][14][15][16] or by inserting buffer layers between BSO epilayers and typical substrates 12,[17][18][19] to release the lattice mismatch strain.…”