Prediction of high-mobility two-dimensional electron gas at KTaO3-based heterointerfaces

First-principles calculations are performed to explore the possibility of generating the two-dimensional electron gas (2DEG) at the interface between LaGaO3/KTaO3 and NdGaO3/KTaO3 (001) heterostructures. Two different models - i.e., the superlattice model and the thin film model - are used to conduct a comprehensive investigation of the origin of charge carriers. For the symmetric superlattice model, the LaGaO3 (or NdGaO3) film is nonpolar. The 2DEG with carrier density on the order of 10(14)cm(-2) originates from the Ta d(xy) electrons contributed by both LaGaO3 (or NdGaO3) and KTaO3. For the thin film model, large polar distortions occur in the LaGaO3 and NdGaO3 layer, which entirely screens the built-in electric field and prevents electrons from transferring to the interface. Electrons of KTaO3 are accumulated at the interface, contributing to the formation of the 2DEG. All the heterostructures exhibit conducting properties regardless of the film thickness. Compared with the Ti d(xy) electrons in SrTiO3-based heterostructures, the Ta d(xy) electrons have small effective mass and they are expected to move with higher mobility along the interface. These findings reveal the promising applications of 2DEG in novel nanoelectronic devices.