Terahertz Electrical Characteristics of Heavily Doped n-GaAs Thin Films

We have measured the frequency-dependent optical and electrical constants of heavily doped n-GaAs thin films from 0.2 to 2.5 THz using terahertz time-domain spectroscopy. Two heavily doped GaAs thin films were grown on semi-insulating GaAs wafers, the target densities of which were 0.5 $\times$ 10$^{18}$ cm$^{-3}$ and 1 $\times$ 10$^{18}$ cm$^{-3}$. The power absorptions of these samples were measured and their conductivities were obtained through subsequent analysis. The results were fitted to the Drude theory, which yielded the carrier densities and mobilities. The mobility was found to be smaller as the carrier density increased and agreed with the literature values.