Modeling terahertz magneto-optical spectroscopic ellipsometry with conductive sheet approximation for semiconductor thin films

We present a simplified model for analyzing the reflection coefficients of anisotropic semiconductor ultrathin films in terahertz magneto-optical ellipsometry. Derived from electromagnetic boundary conditions, the model is valid when the film thickness is much smaller than the wavelength. Its applicability is demonstrated through terahertz time-domain spectroscopic ellipsometry of two doped GaAs thin films under an external magnetic field. The approach allows direct extraction of sheet conductivity spectra and accurately reproduces the observed magneto-optical response, offering a non-invasive method for characterizing various ultrathin-film materials.