Electronic transport properties and stability of 2D electron gases on Si3N4/AlOx//KTaO3 heterostructures

Abstract

We report on the successful stabilization of a two-dimensional electron gas (2DEG) in Si3N4/AlOx//KTaO3(001) heterostructures. Electronic transport measurements reveal that the AlOx layer thickness critically modulates the 2DEG mobility, with an optimal thickness achieving a mobility of μ ≈ 444 cm2 V−1 s−1 at 10 K, which is, despite the amorphous granular nature of the AlOx layers, comparable to epitaxial oxide-based 2DEGs. Thicker AlOx layers reduce mobility and induce a Kondo-like upturn in resistance at low temperatures, which is attributed to oxygen depletion extending into the substrate and enhancing defect scattering. Additionally, the samples remain metallic after six months of exposure to ambient conditions, with high-mobility samples maintaining stable carrier densities and mobilities and experiencing only minor increases in sheet resistance over time. These findings highlight the potential of KTaO3 2DEGs for long-term electronic applications, providing valuable insights for optimizing oxide heterostructures for future device technologies.