How a Ferroelectric Layer Can Tune a Two-Dimensional Electron Gas at the Interface of LaInO₃ and BaSnO₃: A First-Principles Study

The emerging interest in two-dimensional electron gases (2DEGs), formed at interfaces between two insulating oxide perovskites, poses a crucial fundamental question in view of future electronic devices. In the framework of density-functional theory, we investigate the possibility to control the characteristics of the 2DEG formed at the LaInO3/BaSnO3 interface by including a ferroelectric layer. To do so, we consider BaTiO3 as a prototype example and examine how the orientation of the ferroelectric polarization impacts density and confinement of the 2DEG. We find that aligning the ferroelectric polarization toward (outward) the LaInO3/BaSnO3 interface leads to an accumulation (depletion) of the interfacial 2DEG. Varying its magnitude, we find a linear effect on the 2DEG charge density that is confined within the BaSnO3 side. Analysis of the optimized geometries reveals that inclusion of the ferroelectric layer makes structural distortions at the LaInO3/BaSnO3 junction less pronounced, which, in turn, enhances the 2DEG density. Thicker ferroelectric layers allow for reaching higher polarization magnitude. We discuss the mechanisms behind all these findings and rationalize how the characteristics of both 2DEGs and 2D hole gases can be controlled in the considered heterostructures. Overall, our results can be generalized to other combinations of ferroelectric, polar, and nonpolar materials.