A comparison study of electronical and photoelectrical properties of electron gases at (1 0 0), (1 1 0) and (1 1 1) LaAlO3/SrTiO3 interfaces

Abstract

(1 0 0), (1 1 0) and (1 1 1) LaAlO3/SrTiO3 (LAO/STO) interfaces show similar high mobility conduction. Here, we compare electronic transport and photoconductivity properties of electron gases at the three interfaces, considering their different polar continuity at the interface and the crystallographic symmetry. Epitaxial LAO films were grown on STO (1 0 0), (1 1 0) and (1 1 1) substrates by laser molecular beam epitaxy. All the electron gases at the interfaces exhibit metallic behaviors with close sheet carrier density (1013–1014 cm−2), the electron gas at (1 0 0) interface presents the highest mobility, which is almost one order of magnitude higher than that at (1 1 1) interface below 70 K. At lower temperatures, all the electron gases show obvious photoelectrical response to visible light illumination. Light-assisted Hall measurements indicate distinctly different mechanisms for the photoconductivity of electron gases at the three interfaces. Our results can assist the understanding of the high mobility of electron gases at oxide interfaces, which will be helpful to optimize the electronic properties for device applications.