Rastogi, A. and Pulikkotil, J. J. and Budhani, R. C.
(2014)
Enhanced persistent photoconductivity in delta-doped LaAIO(3)/SrTiO3 heterostructures.
Physical Review B, 89 (12).
ISSN 1098-0121
Abstract
We report the effect of delta doping at the LaAlO3/SrTiO3 interface with LaMnO3 monolayers on the photoconducting (PC) state. The PC is realized by exposing the samples to broadband optical radiation of a quartz lamp and 325 and 441 nm lines of a He-Cd laser. Along with the significant modification in electrical transport which drives the pure LaAlO3/SrTiO3 interface from metal-to-insulator with increasing LaMnO3 sub-monolayer thickness, we also observe an enhancement in the photoresponse and relaxation time constant. A possible scenario for the PC based on defect clusters, random potential fluctuations, and large lattice relaxation models, along with the role of structural phase transition in SrTiO3, is discussed. For pure LaAlO3/SrTiO3, the photoconductivity appears to originate from interband transitions between Ti-derived 3d bands which are e(g) in character and 0 2p-Ti t(2g) hybridized bands. The band structure changes significantly when fractional layers of LaMnO3 are introduced. Here the Mn eg bands (approximate to-1.5 eV above the Fermi energy) within the photoconducting gap lead to a reduction in the photoexcitation energy and a gain in overall photoconductivity.
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