Density functional theory study on the formation mechanism and electrical properties of two-dimensional electron gas in biaxial-strained LaGaO$$_3$$/BaSnO$$_3$$ heterostructure

AbstractThe two-dimensional electron gas (2DEG) in BaSnO$$_3$$ 3 -based heterostructure (HS) has received tremendous attention in the electronic applications because of its excellent electron migration characteristic. We modeled the n-type (LaO)$$^+$$ + /(SnO$$_2$$ 2 )$$^0$$ 0 interface by depositing LaGaO$$_3$$ 3 film on the BaSnO$$_3$$ 3 substrate and explored strain effects on the critical thickness for forming 2DEG and electrical properties of LaGaO$$_3$$ 3 /BaSnO$$_3$$ 3 HS system using first-principles electronic structure calculations. The results indicate that to form 2DEG in the unstrained LaGaO$$_3$$ 3 /BaSnO$$_3$$ 3 HS system, a minimum thickness of approximately 4 unit cells of LaGaO$$_3$$ 3 film is necessary. An increased film thickness of LaGaO$$_3$$ 3 is required to form the 2DEG for -3%-biaxially-strained HS system and the critical thickness is 3 unit cells for 3%-baxially-strained HS system, which is caused by the strain-induced change of the electrostatic potential in LaGaO$$_3$$ 3 film. In addition, the biaxial strain plays an important role in tailoring the electrical properties of 2DEG in LaGaO$$_3$$ 3 /BaSnO$$_3$$ 3 HS syestem. The interfacial charge carrier density, electron mobility and electrical conductivity can be optimized when a moderate tensile strain is applied on the BaSnO$$_3$$ 3 substrate in the ab-plane.