Characterization of optically dense, doped semiconductors by reflection THz time domain spectroscopy

We present reflection THz-time domain spectroscopy measurements of the complex conductivity of $n$ -type, 0.038 Ω cm GaAs and $n$ -type, 0.22 Ω cm Si wafers. These measurements clearly demonstrate the efficacy of the reflection technique on highly conductive, optically dense samples and approach the precision of THz–TDS transmission measurements. Because the THz-bandwidth, reflection measurements extend beyond the carrier collision frequency, we obtain direct measures of the mobility and the carrier number density.