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First-principles surface calculations for monoclinic Ga<sub>2</sub>O<sub>3</sub> and Al<sub>2</sub>O<sub>3</sub> and consequences for cracking of (Al<sub>x</sub>Ga<sub>1-x</sub>)<sub>2</sub>O<sub>3</sub> films

ORAL

Abstract

The wide-bandgap semiconductor Ga2O3 is a promising candidate for high-power electronics. Alloying with Al for (AlxGa1-x)2O3 films enables heterostructures that are essential for device applications. However, the limited thickness of (AlxGa1-x)2O3 films grown on Ga2O3 substrates is a serious obstacle. Here we employ first-principles calculations to determine the brittle fracture toughness of such films for three growth orientations of the monoclinic structure: [100], [010], and [001].1 Surface energies and elastic constants are computed for the end compounds—monoclinic Ga2O3 and Al2O3—and used to interpolate to (AlxGa1-x)2O3 alloys. The appropriate crack plane for each orientation is determined, and the corresponding critical thicknesses are calculated based on Griffith’s theory. Our in-depth analysis of surface energies for both relaxed and unrelaxed surfaces provides important insights into the factors that determine the relative stability of different surfaces. A key conclusion is that the critical thickness is largest for (AlxGa1-x)2O3 films grown along [100].

1. Sai Mu, Mengen Wang, Hartwin Peelaers, Chris G. Van de Walle, APL Materials 8, 091105 (2020).

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Presenters

  • Sai Mu

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

Authors

  • Sai Mu

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

  • Mengen Wang

    Materials Department, University of California, Santa Barbara

  • Hartwin Peelaers

    Department of Physics and Astronomy, University of Kansas, 2. Department of Physics and Astronomy, University of Kansas, University of Kansas

  • Chris Van de Walle

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