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Title: Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO{sub 3}/SrTiO{sub 3} superlattices: coexistence of Auger recombination and single-carrier trapping

Abstract

We report emerging photoluminescence (PL) of bilayer two-dimensional electron gases (2DEG) in LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) systems. A strong blue PL emerges in bilayer-2DEGs in LAO/STO/LAO/STO which doesn’t show in LAO/STO. PL band in bilayer-2DEGs includes both nearly temperature independent Auger recombination and temperature dependent free electron trapping while it crossovers from Auger recombination to single carrier trapping in LAO/STO. The PL signal of free electron trapping appears at high temperatures and it is much stronger than Auger recombination in the conducting channel in bilayer 2DEGs. This observation shows that high mobility carriers dominate the carrier dynamics in bilayer-2DEGs in LAO/STO superlattices.

Authors:
;  [1];  [2];  [1];  [2];  [2];  [3];  [4]
  1. NUSNNI-Nanocore, National University of Singapore, 117411 Singapore (Singapore)
  2. (Singapore)
  3. Department of Physics, National University of Singapore, 117542 Singapore (Singapore)
  4. (IMRE), A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)
Publication Date:
OSTI Identifier:
22493921
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 5; Journal Issue: 6; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINATES; AUGER EFFECT; CHARGE CARRIERS; ELECTRONS; EMISSION SPECTROSCOPY; LANTHANUM OXIDES; LAYERS; MOBILITY; PHOTOLUMINESCENCE; RECOMBINATION; STRONTIUM TITANATES; SUPERLATTICES; TEMPERATURE DEPENDENCE; TRAPPING; TWO-DIMENSIONAL SYSTEMS

Citation Formats

Ma, H. J. Harsan, E-mail: a0086305@nus.edu.sg, Ariando, Department of Physics, National University of Singapore, 117542 Singapore, Venkatesan, T., Department of Physics, National University of Singapore, 117542 Singapore, Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore, Wang, S. J., and Institute of Materials Research and Engineering. Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO{sub 3}/SrTiO{sub 3} superlattices: coexistence of Auger recombination and single-carrier trapping. United States: N. p., 2015. Web. doi:10.1063/1.4923320.
Ma, H. J. Harsan, E-mail: a0086305@nus.edu.sg, Ariando, Department of Physics, National University of Singapore, 117542 Singapore, Venkatesan, T., Department of Physics, National University of Singapore, 117542 Singapore, Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore, Wang, S. J., & Institute of Materials Research and Engineering. Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO{sub 3}/SrTiO{sub 3} superlattices: coexistence of Auger recombination and single-carrier trapping. United States. doi:10.1063/1.4923320.
Ma, H. J. Harsan, E-mail: a0086305@nus.edu.sg, Ariando, Department of Physics, National University of Singapore, 117542 Singapore, Venkatesan, T., Department of Physics, National University of Singapore, 117542 Singapore, Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore, Wang, S. J., and Institute of Materials Research and Engineering. Mon . "Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO{sub 3}/SrTiO{sub 3} superlattices: coexistence of Auger recombination and single-carrier trapping". United States. doi:10.1063/1.4923320.
@article{osti_22493921,
title = {Temperature dependence of photoluminescence spectra of bilayer two-dimensional electron gases in LaAlO{sub 3}/SrTiO{sub 3} superlattices: coexistence of Auger recombination and single-carrier trapping},
author = {Ma, H. J. Harsan, E-mail: a0086305@nus.edu.sg and Ariando and Department of Physics, National University of Singapore, 117542 Singapore and Venkatesan, T. and Department of Physics, National University of Singapore, 117542 Singapore and Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore and Wang, S. J. and Institute of Materials Research and Engineering},
abstractNote = {We report emerging photoluminescence (PL) of bilayer two-dimensional electron gases (2DEG) in LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) systems. A strong blue PL emerges in bilayer-2DEGs in LAO/STO/LAO/STO which doesn’t show in LAO/STO. PL band in bilayer-2DEGs includes both nearly temperature independent Auger recombination and temperature dependent free electron trapping while it crossovers from Auger recombination to single carrier trapping in LAO/STO. The PL signal of free electron trapping appears at high temperatures and it is much stronger than Auger recombination in the conducting channel in bilayer 2DEGs. This observation shows that high mobility carriers dominate the carrier dynamics in bilayer-2DEGs in LAO/STO superlattices.},
doi = {10.1063/1.4923320},
journal = {AIP Advances},
number = 6,
volume = 5,
place = {United States},
year = {Mon Jun 15 00:00:00 EDT 2015},
month = {Mon Jun 15 00:00:00 EDT 2015}
}
  • We report magnetotransport properties of double heterointerfaces in LaAlO{sub 3}/SrTiO{sub 3}/LaAlO{sub 3}/SrTiO{sub 3}(001) (LAO/STO/LAO/STO). A strong nonlinearity in the Hall resistivity is found when the temperature is below 80 K. This effect is attributed to multichannel conduction of interfacial charges generated in double heterostructures of LAO/STO where two-dimensional electron gas (2DEG) is produced. The multichannel conduction is confirmed by back gating modulation of Hall effect. Our result suggests the possibility to achieve coupled bilayer 2DEG layers in LAO/STO superlattices.
  • The voltage-spectral density S{sub V} (f) of the 2-dimensional electron gas formed at the interface of LaAlO{sub 3}/SrTiO{sub 3} has been thoroughly investigated. The low-frequency component has a clear 1/f behavior with a quadratic bias current dependence, attributed to resistance fluctuations. However, its temperature dependence is inconsistent with the classical Hooge model, based on carrier-mobility fluctuations. The experimental results are, instead, explained in terms of carrier-number fluctuations, due to an excitation-trapping mechanism of the 2-dimensional electron gas.
  • Cited by 41
  • Recently a metallic state was discovered at the interface between insulating oxides, most notably LaAlO{sub 3} and SrTiO{sub 3}. Properties of this two-dimensional electron gas (2DEG) have attracted significant interest due to its potential applications in nanoelectronics. Control over this carrier density and mobility of the 2DEG is essential for applications of these unique systems, and may be achieved by epitaxial strain. However, despite the rich nature of strain effects on oxide materials properties, such as ferroelectricity, magnetism, and superconductivity, the relationship between the strain and electrical properties of the 2DEG at the LaAlO{sub 3}/SrTiO{sub 3} heterointerface remains largely unexplored.more » Here, we use different lattice constant single-crystal substrates to produce LaAlO{sub 3}/SrTiO{sub 3} interfaces with controlled levels of biaxial epitaxial strain. We have found that tensile-strained SrTiO{sub 3} destroys the conducting 2DEG, while compressively strained SrTiO{sub 3} retains the 2DEG, but with a carrier concentration reduced in comparison to the unstrained LaAlO{sub 3}/SrTiO{sub 3} interface. We have also found that the critical LaAlO{sub 3} overlayer thickness for 2DEG formation increases with SrTiO{sub 3} compressive strain. Our first-principles calculations suggest that a strain-induced electric polarization in the SrTiO{sub 3} layer is responsible for this behavior. The polarization is directed away from the interface and hence creates a negative polarization charge opposing that of the polar LaAlO{sub 3} layer. This behavior both increases the critical thickness of the LaAlO{sub 3} layer, and reduces carrier concentration above the critical thickness, in agreement with our experimental results. Our findings suggest that epitaxial strain can be used to tailor 2DEGs properties of the LaAlO{sub 3}/SrTiO{sub 3} heterointerface.« less