Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 9: Focus Session: Oxide Semiconductors for Novel Devices II

HL 9.9: Vortrag

Montag, 1. April 2019, 17:00–17:15, H34

Thermodynamics and electronic structure of low-index β-Ga2O3 surfaces — •Konstantin Lion1,2, Sergey V. Levchenko3,2,4, Matthias Scheffler2, and Claudia Draxl1,21Humboldt-Universität zu Berlin, Berlin, DE — 2Fritz-Haber-Institut der MPG, Berlin, DE — 3Skolkovo Innovation Center, Moscow, RU — 4NUST MISIS, Moscow, RU

The surface properties of β-Ga2O3 play a vital role in epitaxial growth, electrical contacts, and gas sensors, but are still not well understood. In this work, we study the stability and electronic structure of several non-polar low-index surfaces of β-Ga2O3 using ab initio atomistic thermodynamics. Employing the efficient high-precision all-electron code FHI-aims, we perform density-functional-theory calculations with the HSE06 hybrid exchange-correlation functional. Numerous surface free energies are calculated, also including vibrational contributions. We find that the (100) surface is the most stable one, in agreement with previous reports [1], but, quite suprisingly, it is followed closely by the (201) surface. Here, the topmost surface layers are significantly flattened upon relaxation, reducing the surface energy to 40 % of the value of the unrelaxed surface. This result explains recent experimental findings where (201) facets were found to form during homoepitaxial growth on off-oriented β-Ga2O3 (100) substrates [2]. For this surface the electronic structure also reveals a strong surface resonance at the top of the valence band.

[1] V.M. Bermudez, Chem. Phys. 323, 193 (2006).

[2] R. Schewski et al., APL Materials 7 (2019), in print.

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