Controlling the density of electrons in the 2DEG at complex oxide interfaces

ORAL

Abstract

The formation of a two-dimensional electron gas (2DEG) at the interface between two insulators, SrTiO$_{\mathrm{3\thinspace }}$(STO) and LaAlO$_{\mathrm{3}}$ (LAO), has sparked huge interest in oxide electronics. In spite of almost a decade of research, the mechanisms that determine the density of this 2DEG have not yet been unravelled. The polar discontinuity at the STO/LAO interface can in principle sustain an electron density of 3.3x10$^{\mathrm{14\thinspace }}$cm$^{\mathrm{-2\thinspace }}$(0.5 electrons per unit cell). However, experimentally observed densities are more than an order of magnitude lower. Using a combination of first-principles and Schr\"{o}dinger-Poisson simulations we investigate the origin of the electrons in the 2DEG at the STO/LAO interface. We analyze the asymmetric nature of the heterostructures, i.e., the inability to form a second LAO/STO interface that is a mirror image of the first, and the effects of passivation of the LAO surface. Our results apply to oxide interfaces in general, and explain why the SrTiO$_{\mathrm{3}}$/GdTiO$_{\mathrm{3\thinspace }}$interface has been found to exhibit the full density of 0.5 electrons per unit cell.

*This work has been supported by the ARO and NSF.

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Authors

  • Chris Van de Walle

    • University of California at Santa Barbara
    • Materials Department, University of California, Santa Barbara
    • Materials Department, University of California Santa Barbara
    • University of California, Santa Barbara
    • University of California, Santa Barbara Materials Department
    • University of California Santa Barbara
    • Materials department and materials Research Lab, University of California Santa Barbara, California 93106-5050, USA
    • Materials Department, University of California at Santa Barbara

  • Lars Bjaalie

    • Materials Department, University of California, Santa Barbara

  • Luke Gordon

    • University of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara

  • Anderson Janotti

    • University of California Santa Barbara
    • Materials Department, University of California, Santa Barbara