Acoustic phonon characteristics of (001) and (2¯01) β-Ga2O3 single crystals investigated with Brillouin–Mandelstam light scattering spectroscopy

We report an investigation of the bulk acoustic phonons of (001) and (2¯01) β-Ga2O3 ultra-wide bandgap single crystals using Brillouin–Mandelstam spectroscopy. Pronounced anisotropy in the acoustic phonon dispersion and velocities was observed across different crystal directions. The measured, polarization-branch averaged, acoustic phonon velocities for the crystallographic directions of interest suggest that the difference in phonon velocities contributes to the anisotropy of the reported thermal conductivity of β-Ga2O3, in addition to possible variations in phonon lifetimes. The obtained information for acoustic phonons can be used for developing accurate theoretical models of phonon scattering and optimization of thermal and electrical transport in this technologically important ultra-wide bandgap semiconductor.