[en] Heteroepitaxial growth of BaSnO₃ and Ba_1−xLa_xSnO₃ (x = 7%) lanthanum doped barium stannate thin films on different perovskite single crystal (SrTiO₃ (001) and SmScO₃ (110)) substrates has been achieved by pulsed laser deposition under optimized deposition conditions. X-ray diffraction measurements indicate that the films on either of these substrates are relaxed due to the large mismatch and present a high degree of crystallinity with narrow rocking curves and smooth surface morphology while analytical quantification by proton induced X-ray emission confirms the stoichiometric La transfer from a polyphasic target, producing films with measured La contents above the bulk solubility limit. The films show degenerate semiconducting behavior on both substrates, with the observed room temperature resistivities, Hall mobilities, and carrier concentrations of 4.4 mΩ cm, 10.11 cm² V⁻¹ s⁻¹, and 1.38 × 10²⁰ cm⁻³ on SmScO₃ and 7.8 mΩ cm, 5.8 cm² V⁻¹ s⁻¹, and 1.36 × 10²⁰ cm⁻³ on SrTiO₃ ruling out any extrinsic contribution from the substrate. The superior electrical properties observed on the SmScO₃ substrate are attributed to reduction in dislocation density from the lower lattice mismatch