Measurement of the terahertz Faraday effect in III-V semiconductors

We have developed a magneto-optical measurement system in the terahertz region and measured the Faraday effect of III-V semiconductors. The system consists of a cryogen-free superconducting magnet, a refrigerator for samples and a terahertz time-domain spectroscopy system. In this study, we have investigated the magnetic field and temperature dependences of the Faraday ellipticity and rotation angle of Si-doped n-type GaAs. The frequency dependence of the ellipticity and rotation angle is well described by semi classical models, that is, the Drude model and the Boltzmann transport theory around room temperature. However, below ∼150K, both models are not appropriate to describe results because of the appearance of quantum effects.