Absorption anisotropy of orthorhombic single-domain κ-Ga2O3 from infrared to ultraviolet: Phonons and bandgaps

We present the anisotropic dielectric functions and absorption coefficients of orthorhombic single-domain (001) κ-Ga2O3. Single-domain κ-Ga2O3 grown by mist chemical vapor deposition on ε-GaFeO3 was investigated by spectroscopic ellipsometry, from the infrared to the ultraviolet spectral range. We find infrared-active phonon modes of B1 and B2 symmetry. The dielectric functions in the visible–ultraviolet range yield the high frequency dielectric constants ε∞ and the anisotropic fundamental interband transitions at 4.82 and 5.75 eV (εyy), 5.09 eV (εxx), and 5.43 eV (εzz). The results are compared to theoretical calculations, and earlier studies on multi-domain κ-Ga2O3.