Temperature Dependence of the Anisotropic Dielectric Properties of Semiinsulating β-Ga2O3 in the Terahertz Region

We conducted measurements using terahertz timedomain spectroscopy on a semi-insulating bulk sample of (001)oriented beta gallium oxide $\left(\beta-\mathrm{Ga}_{2} \mathrm{O}_{3}\right)$ in the temperature range of $90 \mathrm{~K}$ to $400 \mathrm{~K}$. We analyzed the complex dielectric function parallel to the a-axis $[100]$ and b-axis $[010]$ in the frequency range from 0.2 to 3THz using the Lorentz model. Our analysis enabled us to investigate the temperature dependence of the static dielectric constants and phonon absorption, as well as the anisotropy of $\beta-\mathrm{Ga}_{2} \mathrm{O}_{3}$.