Measurement of complex optical constants of a highly doped Si wafer using terahertz ellipsometry

We propose and demonstrate a terahertz (THz) time-domain spectroscopy combined with ellipsometry. The complex optical constants of a Si wafer with low resistivity are deduced from the measurements of the wave forms of reflected s- and p-polarized THz pulses without reference measurement. The obtained dispersion of refractive index above ∼0.2 THz shows good agreement with that predicted by the Drude theory. The complex optical constants deduced by the THz ellipsometry in the low-frequency region are strongly affected by the slight error of the ellipsometric angle originating mainly from the misalignment of the rotation angles of the polarizer and analyzer.