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HL: Fachverband Halbleiterphysik
HL 28: Focus Session: Heat transport at the nanoscale: theory meets experiment
HL 28.6: Talk
Wednesday, March 20, 2024, 12:00–12:15, EW 203
Ballistic phonon transport in ß-Ga2O3 — •Rüdiger Mitdank1, Robin Ahrling1, Andreas Popp2, Jana Rehm2, Arub Akhtar2, Zbigniew Galazka2, and Saskia Fischer1, 3 — 1Novel Materials Group, Humboldt-Universität zu Berlin, 12489 Berlin, Germany — 2Leibniz Institut für Kristallzüchtung, 12489 Berlin, Germany — 3CSMB, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
The anisotropic thermal conductivity and the phonon mean free path (mfp) in monoclinic ß-Ga2O3 single crystals and homoepitaxial films of several micron were determined using the 3-ω method in the temperature range from 10 K-300 K. Analysis of the phonon mfp shows a dominance of phonon-phonon-Umklapp scattering above 80 K, below which the influence of point-defect scattering is observed. Below 30 K the phonon mfp increases and the dominance of boundary effects and the crossover from resistive to ballistic phonon transport is observed. The measured effective thermal conductivity reaches a maximum of 1000-2000 W/(mK) and decreases with T^3 below 25 K. The resistive and ballistic phonon transport regimes in ß-Ga2O3 are discussed corresponding to the models of Callaway (resistive transport - Fourier limit) and Majumdar (phonon radiative transport - Casimir limit), respectively. The Casimir limit is achieved in very pure Ga2O3 single crystals and homoepitaxial layers.
1. A. Majumdar, Journal of Heat Transfer, 115, 7, 1993; 2. Callaway, J, Phys. Rev. 113, 1046, 1959; 3. H. Casimir, Physica, 5, no. 6, 495, 1938
(funded by the DFG: FI932/10-1 and FI932/11-1).
Keywords: Ballistic phonon transport; Casimir limit; Oxide semiconductors; Thermal properties; Transport properties