Persistent photoconductivity in 2-dimensional electron gases at different oxide interfaces

TL;DR

This study investigates persistent photoconductivity in three oxide interfaces, revealing intrinsic properties and charge confinement that could impact solar energy applications and deepen understanding of oxide interface physics.

Contribution

It provides a comparative analysis of photoconductivity in LaAlO3/SrTiO3, LaGaO3/SrTiO3, and NdGaO3/SrTiO3 interfaces, highlighting the intrinsic nature of persistent photoconductivity.

Findings

Persistent photoconductivity is intrinsic to the studied oxide interfaces.

Charge confinement at the NdGaO3/SrTiO3 interface is similar to LaAlO3/SrTiO3.

Understanding photo-induced electron-hole pairs could advance solar energy conversion.

Abstract

We report on the transport characterization in dark and under light irradiation of three different interfaces: LaAlO3/SrTiO3, LaGaO3/SrTiO3, and the novel NdGaO3/SrTiO3 heterostructure. All of them share a perovskite structure, an insulating nature of the single building blocks, a polar/non- polar character and a critical thickness of four unit cells for the onset of conductivity. The interface structure and charge confinement in NdGaO3/SrTiO3 are probed by atomic-scale- resolved electron energy loss spectroscopy showing that, similarly to LaAlO3/SrTiO3, extra electronic charge confined in a sheet of about 1.5 nm in thickness is present at the NdGaO3/SrTiO3 interface. Electric transport measurements performed in dark and under radiation show remarkable similarities and provide evidence that the persistent perturbation induced by light is an intrinsic peculiar property of the three investigated oxide-based polar/non-polar interfaces. Our work sets a framework for understanding the previous contrasting results found in literature about photoconductivity in LaAlO3/SrTiO3 and highlights the connection between the origin of persistent photoconductivity and the origin of conductivity itself. An improved understanding of the photo- induced metastable electron-hole pairs might allow to shed a direct light on the complex physics of this system and on the recently proposed perspectives of oxide interfaces for solar energy conversion.