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.

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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