Temperature dependence of the Faraday effect of moderately doped semiconductors at terahertz frequencies

The temperature dependence of the Faraday effect of moderately doped n-type Si wafers (1.1 Ω cm) at terahertz frequencies was measured by time domain spectroscopy systematically changing the magnetic field. At temperatures of ∼90 K and below, cyclotron resonances of the free carriers are observed at 4 and 6 T. At temperatures from 90 to 150 K, the values of the ellipticity of the transmitted terahertz wave reach almost unity above 0.4 THz. The temperature dependences of the density and scattering time of the free carriers are deduced by fits of the experimental data to a model taking into account transverse and longitudinal effective masses of the valleys for the free carriers in Si.