Novel photo-conducting state and its perturbation by electrostatic fields in oxide-based two-dimensional electron gas

Abstract

The two-carrier transport model as proposed for the two-dimensional electron gas formed at the interfaces of oxide heterostructures is investigated by means of a combined perturbation of near ultra-violet radiation and electrostatic field, applied both separately and simultaneously. Comparison of the photo-response of the prototype systems such as the band insulator LaAlO3 and Mott insulator LaTiO3 films on TiO2 terminated SrTiO3 show remarkably similarities. Two types of non-equilibrium carriers are generated in each system, having a signature of a particular type of perturbation characterized by distinctly different relaxation process. While, the photo-conducting state diminishes in a stretched exponential manner, with a temperature dependent activation energy varying from few tens of meV to ~ 1 to 2 meV on lowering the temperature, and a relaxation time of several hours, the recovery from electrostatic gating occurs in milli-seconds time scale. An attempt is also made to explain the experimental observations using the ab-initio density functional calculations. The calculations show that the electronic transitions associated with near ultra-violet radiation emerge from bands located at ~ 2 eV above and below the Fermi energy, which are the Ti 3d states of the SrTiO3 substrate, and that from the AlO2 (TiO2) layers of the LaAlO3 (LaTiO3) films, respectively. The slow decay of the photo-current to the unperturbed state is explained in terms of the closely spaced Ti 3dxy states in the lower conduction band, which are manifested as flat bands (or localized states) in the band structure. Such localization leads to increased carrier life-times, through the energy-time relationship of the uncertainty principle.

10 pages, 8 figures

References in corpus (15)

• Magnetic effects at the interface between nonmagnetic oxides
• Coexistence of Magnetic Order and Two-dimensional Superconductivity at LaAlO${}_3$/SrTiO${}_3$ Interfaces
• The role of oxygen vacancies in SrTiO3 at the LaAlO3/SrTiO3 interface
• High Mobility in LaAlO3/SrTiO3 Heterostructures: Origin, Dimensionality and Perspectives
• Origin of charge density at LaAlO3-on-SrTiO3 hetero-interfaces; possibility of intrinsic doping
• Coexistence of superconductivity and ferromagnetism in two dimensions
• Avoiding the polarization catastrophe in LaAlO3 overlayers on SrTiO3(001) through a polar distortion
• Two-dimensional superconductivity at a Mott-Insulator/Band-Insulator interface: LaTiO3/SrTiO3
• Two-dimensional quantum oscillations of the conductance at LaAlO3/SrTiO3 interfaces
• Lattice relaxation, electronic screening, and spin and orbital phase diagram of LaTiO${}_3$/SrTiO${}_3$ superlattices
• Built-in and induced polarization across LaAlO${}_3$/SrTiO${}_3$ heterojunctions
• Parallel electron-hole bilayer conductivity from electronic interface reconstruction
• Multiple conducting carriers generated in LaAlO3/SrTiO3 heterostructures
• Local Ferroelectricity in SrTiO_3 Thin Films
• Vanishing Hall Coefficient in the Extreme Quantum Limit in Photocarrier-Doped SrTiO3

Cited by in corpus (15)

• Hard x-ray photoemission and density functional theory study of the internal electric field in SrTiO3/LaAlO3 oxide heterostructures
• Enhanced persistent photoconductivity in $\delta$-doped LaAlO${}_3$/SrTiO${}_3$ heterostructures
• Enhanced spin-orbit interaction and Kondo scattering in $\delta$-doped LaTiO${}_3$/SrTiO${}_3$ interfaces
• Optically excited multi-band conduction in LaAlO3/SrTiO3 heterostructures
• Photoresponse dynamics in amorphous-LaAlO${}_3$/SrTiO${}_3$ interfaces
• Enhanced spin-orbit coupling and charge carrier density suppression in LaAl1-xCrxO3/SrTiO3 heterointerfaces
• Defect-induced photoluminescence of strontium titanate and its modulation by electrostatic gating
• Metallic Conductance at the Interface of Tri-color Titanate Superlattices
• Evolution of ferromagnetism in two-dimensional electron gas of LaTiO3/SrTiO3
• Signature of enhanced spin-orbit interaction in the magnetoresistance of LaTiO${}_3$/SrTiO${}_3$ interfaces on $\delta$-doping
• Dynamics of photo-generated non-equilibrium electronic states in Ar${}^{+}$ ion irradiated SrTiO${}_3$
• Nanoscale control of LaAlO3/SrTiO3 metal-insulator transition using ultra-low-voltage electron-beam lithography
• Electric field control of photoinduced effect in La${}_{0.7}$Sr${}_{0.3}$MnO${}_3$/LaTiO${}_3$/SrTiO${}_3$ heterostructure
• Kondo effect with tunable spin orbit interaction in LaTiO3/CeTiO3/SrTiO3 heterostructure
• δ-doped LaAlO3-SrTiO3 interface: Electrical transport and characterization of the interface potential