Drude conductivity of highly doped GaAs at terahertz frequencies

Time domain spectroscopy has been used to measure the room temperature transmission of highly doped GaAs in the frequency range from 0.2 to above 3 THz. We studied n- and p-type layers, with carrier densities between ${10}^{16}$ and ${\text{2×10}}^{18}\hspace{0.5em}{\mathrm{cm}}^{\mathrm{-3}},$ which had been grown on undoped GaAs substrates. Transmission spectra could be fitted within experimental error by using a Drude model for the conductivity. Fitted carrier densities for both carrier types and mobilities for p-type GaAs were in good agreement with the results of Hall measurements. In the case of n-GaAs, the optically determined mobility appeared to underestimate slightly the Hall mobility.