Exploring two-dimensional electron (or hole) gas at BaSnO₃/LaInO₃ interfaces: A first-principles study

We explore the formation of a two-dimensional electron gas (2DEG) at interfaces formed by two wide-gap perovskites of emerging interest, i.e. BaSnO₃ (BSO) and LaInO₃ (LIO), the latter being a polar material. For periodic structures, we find that the polar discontinuity at the interface is mainly compensated by an electronic relaxation through a charge transfer from the LIO to the BSO side. This leads to the formation of a 2DEG of Sn-s character, confined within three BSO unit cells (u.c.), and a 2D hole gas, of O-p character confined within one LIO u.c. We also find that structural distortions through octahedra tilts induce a depolarization field to counteract the polar discontinuity. This causes a progressive charge transfer from the LIO to the BSO side beyond a critical thickness of 4 LIO u.c. The polar discontinuity increases with the LIO thickness, leading to a 2DEG density of 0.5 e/u.c-surface. In a non-periodic BSO/LIO interface, the distortions at the BSO side (substrate) are less pronounced. This enhances the polar discontinuity and allows for reaching higher 2DEG densities than in the heterostructure, for a similar LIO thickness and allows an extension of the 2DEG up to 5 u.c. in the BSO substrate compared to 3 u.c. in the heterostructure.