Negative photoconductivity under visible light illumination in LaAlO3/SrTiO3 heterostructures

The electron gas in LaAlO3/SrTiO3 heterostructures typically exhibits positive photoconductivity (PPC). Here, we report negative photoconductivity (NPC) induced by visible light in LaAlO3/SrTiO3 heterostructures grown in low oxygen pressure (similar to 10(-6) Torr). In contrast to the persistent PPC effect in LaAlO3/SrTiO3 heterostructures, the NPC effect is transient and wavelength independent. The origin of the NPC effect can be mainly attributed to enhanced electron scattering from oxygen-vacancy-related electron traps, confirmed by wavelength-dependent photoconductance and light-assisted Hall measurements. Our results provide a deeper insight into the complex interaction between light and oxygen vacancy in oxide electron gas.