Anharmonicity of lattice vibrations in thin film α-Ga2O3 investigated by temperature dependent Raman spectroscopy

Gallium oxide is a promising candidate for several future electronic devices to replace common technologies. For this reason, an understanding of fundamental physical processes is needed. In this work, we investigate the Raman excitations of a α-Ga2O3 thin film under temperature variation from 80 K up to 790 K. This yields detailed information about anharmonic processes in the crystal. For the two dominant phonon modes for each of the two Raman-active phonon mode symmetries (A1g and Eg), model calculations are performed in order to quantify the contributions of different decay mechanisms. It is shown that our experimental data can be well described by the applied theoretical models. The determined coefficients of cubic and quartic decay for both, phonon energy and linewidth, are compared with those from hexagonal GaN and AlN as well as with those from α-Al2O3. We observe that for the two selected phonon modes of α-Ga2O3, the shifts of frequency and broadening under temperature variation are significantly smaller than in GaN and AlN, but similar to α-Al2O3.