Terahertz Time-Domain Ellipsometry of Heavily Doped β-Ga2 O3

Heavily doped $\beta$-Ga$_{2} O_{3}$ single crystal was investigated using terahertz time-domain ellipsometry. $\beta$-Ga$_{2} O_{3}$ is anisotropic, hence, measurements were performed at different sample azimuthal angles. The optical properties were found to be largely influenced by the free carriers than the anisotropic background permittivity, and phonon effects were negligible in the measurement region. Drude model was then used to extract the carrier density and mobility parameters.