Angular-Resolved and Temperature-Dependent Raman Spectroscopy of β and ε-Ga ₂ O ₃

β and ε-phase gallium oxide (Ga2O3) are wide-bandgap semiconductors with promising applications in power electronics and deep-ultraviolet optoelectronics. In this work, systematic Raman spectroscopic investigations, including conventional Raman spectra, angular-resolved polarized Raman spectroscopy, and temperature-dependent Raman measurements, are carried out to elucidate the phonon characteristics and lattice vibrational behavior of β and ε-Ga2O3. For β-Ga2O3, angular-resolved polarized Raman measurements on the (100), (001), and (2̅01) crystal planes reveal pronounced differences in the symmetry, intensity distribution, and angular periodicity of its Raman modes. This indicates that the angular dependence of Raman intensities can serve as an effective spectroscopic approach for crystal-plane identification. For ε-Ga2O3 thin films, the Raman modes exhibited a much weaker angular dependence and smooth temperature-induced frequency shifts without evidence of structural phase transitions, reflecting excellent lattice stability. These findings provide valuable insights into the lattice dynamics of Ga2O3 polymorphs and establish a robust experimental basis for the structural characterization and phase identification of Ga2O3-based materials and devices.