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

Abstract

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 the 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