Far-Infrared Resonant Faraday Effect in Semiconductors

Abstract

We have studied resonant Faraday effect (RFE) related to the intraband transitions in various semiconductors at low temperature through direct measurements for the Faraday rotation angle and ellipticity of the probe far-infrared (FIR) light. Through cyclotron resonance due to electrons in a thin n-InSb sample and two-dimensional electrons in the interface of GaAs/AlGaAs as well as the impurity absorption by donors in the n-InSb, we have made clear that RFE is dominated by the off-diagonal components of dielectric tensor. Experimental results for bulk n-InSb samples with various thicknesses have revealed a lot of properties of RFE as saturation effect on absorption. The oscillatory spectra induced by several twirls of the polarization plane have been observed in the extremely thick InSb sample. Spectra of the thick n-InSb also show high sensitivity of ellipticity for interference of circularly polarized lights. Besides, making use of the characteristic behavior on RFE, we can classify absorption lines due to impurities in Ge, i.e., the electron-type absorption or the hole-type one. By referring the experimental results to the theory based on Lorentz-oscillator model, we have made clear some characteristic features on RFE.