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arXiv · 2403.11341

Resistive and ballistic phonon transport in $\beta$-Ga$_2$O$_3$

R. Ahrling·R. Mitdank·A. Popp·J. Rehm·A. Akhtar·Z. Galazka·S. F. Fischer
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Abstract

The anisotropic thermal conductivity and the phonon mean free path (mfp) in monoclinic $\beta$-Ga$_2$O$_3$ single crystals and homoepitaxial films of several $\mu$m were determined using the 3$\omega$-method in the temperature range from 10K-300 K. The measured effective thermal conductivity of both, single crystal and homoepitaxial films are in the order of 20 W/(mK) at room temperature, below 30 K it increases with a maximum of 1000 to 2000 W/(mK) and decreases with T$^3$ below 25 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 until it is limited by the total $\beta$-Ga$_2$O$_3$ sample size. A crossover from resistive to ballistic phonon transport is observed below 20 K and boundary effects of the total sample size become dominant. This reveals that the homoepitaxial film-substrate interface is highly phonon-transparent. The resistive and ballistic phonon transport regimes in $\beta$-Ga$_2$O$_3$ are discussed corresponding to the models of Callaway and Majumdar, respectively.

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R. Ahrling, R. Mitdank, A. Popp, J. Rehm, A. Akhtar, Z. Galazka, S. F. Fischer. 2024-03-17. Resistive and ballistic phonon transport in $\beta$-Ga$_2$O$_3$. https://doi.org/10.1103/physrevb.110.085302

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