Vibrational and electron-phonon coupling properties of $$β$$-Ga₂O₃ from first-principles calculations: Impact on the mobility and breakdown field

Journal Article · Wed Jan 16 00:00:00 EST 2019 · AIP Advances

DOI:https://doi.org/10.1063/1.5055238· OSTI ID:1543891

Mengle, K. A. ^[1]; Kioupakis, E. ^[1]

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1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Materials Science and Engineering

The wide band gap semiconductor $$β$$-Ga₂O₃ shows promise for applications in high-power and high-temperature electronics. The phonons of $$β$$-Ga₂O₃ play a crucial role in determining its important material characteristics for these applications such as its thermal transport, carrier mobility, and breakdown voltage. In this work, we apply predictive calculations based on density functional theory and density functional perturbation theory to understand the vibrational properties, phonon-phonon interactions, and electron-phonon coupling of $$β$$-Ga₂O₃. We calculate the directionally dependent phonon dispersion, including the effects of LO-TO splitting and isotope substitution, and quantify the frequencies of the infrared and Raman-active modes, the sound velocities, and the heat capacity of the material. Our calculated optical-mode Grüneisen parameters reflect the anharmonicity of the monoclinic crystal structure of $$β$$-Ga₂O₃ and help explain its low thermal conductivity. We also evaluate the electron-phonon coupling matrix elements for the lowest conduction band to determine the phonon mode that limits the mobility at room temperature, which we identified as a polar-optical mode with a phonon energy of 29 meV. We further apply these matrix elements to estimate the breakdown field of $$β$$-Ga₂O₃. Our theoretical characterization of the vibrational properties of $$β$$-Ga₂O₃ highlights its viability for high-power electronic applications and provides a path for experimental development of materials for improved performance in devices.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE Office of Science (SC)
• OSTI ID: 1543891
• Journal Information: AIP Advances, Vol. 9, Issue 1; ISSN 2158-3226
• Publisher: American Institute of Physics (AIP)
• Country of Publication: United States
• Language: English

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