From LaAlO3/SrTiO3 to LaAlO3/KNbO3: Improving the transport properties of two-dimensional electronic gas in created+1/+1 interfaces

摘要

The discovery of two-dimensional electron gases at LaAlO3/SrTiO3 heterointerface makes it a promising candidate for new generation of nano-devices. Further enhance of interfacial transport properties is the main challenge. To increase the limit of interfacial carrier densities of two-dimensional electron gas (2DEG) of well-studied LaAlO3/SrTiO3 heterostructure from 0.5 to 1 e(-) per unit cell, we replaced substrate SrTiO3 by KNbO3 to acquire the + 1/+ 1 interface with one extra electron donor and less localized valence electrons. First-principles calculations are used to study (LaBO3)(m)/(KNbO3)(6)(.5) (B = Al, Ga; m = 2-8) heterostructures. The studied heterostructures all show n-type metallic state without critical thickness, and the distribution of charge densities of different monolayers can be modulated by the polarization effect of KNbO3. The interfacial carrier density of studied heterostructures perform one order of magnitude larger than LaAlO3/SrTiO3 because of the increased intrinsic carrier limit. With the increase of LaBO3 (B = Al, Ga) layer thickness, the interfacial carrier density rises up to 1.26 x 10(14) cm(-2), and the electron effective masses decrease monotonically, resulting in higher carrier mobility and around 6 times larger electrical conductivity. This work proved an effective approach for tuned interfacial 2DEG and future device engineering.