Photoelectrical properties of insulating LaAlO3-SrTiO3 interfaces

We report photoconductivity of an insulating LaAlO3-SrTiO3 (LAO-STO) heterointerface. Persistent photocurrent induced by a 514 nm laser at room temperature is significant, which is attributed to carriers trapped by a built-in potential well at the interface. Further studies of photoconductivity of the insulating LAO-STO interface performed with a monochrometer demonstrate the photoelectrical response not only in the ultraviolet region but also in the visible and infrared regions. The extrinsic photoconductivity indicates several midgap states located in the insulating LAO-STO interface. Our results provide a deep understanding of the band structure of the insulating LAO-STO heterointerface and promising applications as optoelectronic devices.