Two-dimensional n/p type carriers at the interface of LaAlO₃/KTaO₃ heterostructures

This study employs first-principles calculations to investigate the behavior of two-dimensional carriers at the interfaces and surfaces of polar/polar LaAlO₃/KTaO₃ (LAO/KTO) heterostructures. Unlike traditional LaAlO₃/SrTiO₃ (LAO/STO) polar/nonpolar heterostructures with LaAlO₃ unit-cell thickness-dependent critical conductive behavior, the LaAlO₃/KTaO₃ heterostructures are demonstrated to have intrinsic two-dimensional carriers with carrier concentrations reaching up to 10¹⁴ cm^-2, significantly higher than those observed in LaAlO₃/SrTiO₃ systems. Furthermore, in contrast to traditional sandwich heterostructure models, the single-interface LaAlO₃/KTaO₃ heterostructures exhibit no bandgap dependence on the LaAlO₃ thickness. These phenomena arise from the bipolar characteristics of the LaAlO₃/KTaO₃ system, and it can introduce increased carrier density and reduce symmetry within the single-interface polar heterostructure. Simulation results also show that applying in-plane strain can suppress and even reverse the n/p-type of two-dimensional carriers at the interfaces. Additionally, the presence of oxygen vacancies enhances carrier accumulation by redistributing the internal polarization field of the heterostructures. Overall, this research offers a comprehensive elucidation of the behaviors and formation mechanisms for n/p-type two-dimensional carriers in polar/polar LaAlO₃/KTaO₃ heterostructures and provides potential strategies for manipulating these two-dimensional carriers in relevant materials and devices.