Reversible Photomodulation of Two-Dimensional Electron Gas in LaAlO<sub>3</sub>/SrTiO<sub>3</sub> Heterostructures

Abstract

Long-lived photoinduced conductance changes in LaAlO3/SrTiO3 (LAO/STO) heterostructures enable theiruse inoptoelectronic memory applications. However, it remains challengingto quench the persistent photoconductivity (PPC) instantly and reproducibly,which limits the reversible optoelectronic switching. Herein, we demonstratea reversible photomodulation of two-dimensional electron gas (2DEG)in LAO/STO heterostructures with high reproducibility. By irradiatingUV pulses, the 2DEG at the LAO/STO interface is gradually transformedto the PPC state. Notably, the PPC can be completely removed by watertreatment when two key requirements are met: (1) the moderate oxygendeficiency in STO and (2) the minimal band edge fluctuation at theinterface. Through our X-ray photoelectron spectroscopy and electricalnoise analysis, we reveal that the reproducible change in the conductivityof 2DEG is directly attributed to the surface-driven electron relaxationin the STO. Our results provide a stepping-stone toward developingoptically tunable memristive devices based on oxide 2DEG systems.