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

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.

11 pages, 7 figures

References in corpus (6)

• Origin of charge density at LaAlO3-on-SrTiO3 hetero-interfaces; possibility of intrinsic doping
• Avoiding the polarization catastrophe in LaAlO3 overlayers on SrTiO3(001) through a polar distortion
• Oxide Heterostructures for Efficient Solar Cells
• Strong electronic correlation and strain effects at the interfaces between polar and nonpolar complex oxides
• Low temperature metallic state induced by electrostatic carrier doping of SrTiO${}_3$
• Recombination kinetics of a dense electron-hole plasma in strontium titanate

Cited by in corpus (8)

• Photoresponse dynamics in amorphous-LaAlO${}_3$/SrTiO${}_3$ interfaces
• Observation of a two-dimensional electron gas at CaTiO${}_3$ film surfaces
• Carrier-number fluctuations in the 2-dimensional electron gas at the LaAlO3/SrTiO3 interface
• Light induced decoupling of electronic and magnetic properties in manganites
• Infrared ellipsometry study of the photo-generated charge carriers at the (001) and (110) surfaces of SrTiO${}_3$ crystals and the interface of corresponding LaAlO${}_3$/SrTiO${}_3$ heterostructures
• Observation of strontium segregation in LaAlO${}_3$/SrTiO${}_3$ and NdGaO${}_3$/SrTiO${}_3$ oxide heterostructures by X-ray photoemission spectroscopy
• Infrared study of the quasi-two-dimensional electron system at the interface between SrTiO${}_3$ and crystalline or amorphous LaAlO${}_3$
• Quantum oscillations in an optically-illuminated two-dimensional electron system at the LaAlO${}_3$/SrTiO${}_3$ interface