SKM 2023 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 21: Thermal properties
HL 21.3: Talk
Tuesday, March 28, 2023, 11:30–11:45, POT 251
Origin of thermal anisotropy in monoclinic β−Ga2O3 — •Markus R. Wagner1,2, Benjamin M. Janzen2, Zbigniew Galazka3, Bartlomiej Graczykowski4, Kai Xu5, Ricardo Rurali5, and Juan Sebastian Reparaz5 — 1Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany — 2Technische Universität Berlin, Germany — 3Leibniz-Institut für Kristallzüchtung, Berlin, Germany — 4Faculty of Physics, Adam Mickiewicz University, Poland — 5Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Spain
We present a comprehensive all-optical contact-free investigation of the anisotropy of GHz and THz phonon-mediated material properties in β−Ga2O3. The full thermal conductivity tensor is determined by a newly developed all-optical experimental technique that enables sub-degree angular resolution in the measurement of the in-plane anisotropy of the thermal conductivity based on anisotropic frequency-domain thermoreflectance. Using this novel approach we determine the in-plane anisotropy of the thermal conductivity and its anisotropy ratio with high precision. The anisotropy of the sound velocity, elasticity, and Young modulus is measured by polarized, angular-resolved Brillouin light scattering of GHz acoustic phonons. Based on the experimental anisotropy maps of acoustic phonon velocities and thermal conductivity in combination with calculations of the phonon density of states and phonon lifetimes, we discuss the individual contributions of phonon velocities and phonon lifetimes to the anisotropy of the thermal conductivity.