Low-Temperature Scattering in InSb Measured by Infrared Faraday Rotation

Low-temperature electron-impurity scattering has been measured in $n$-type InSb using both far-infrared Faraday rotation and ellipticity. The experimental results at 5°K using 337- and 119-μm radiation yielded scattering times of 3-5×${10}^{-12\mathrm{}}$ sec, which are in good agreement with earlier measurements of scattering using cyclotron resonance linewidths. The results show that dc theory cannot be used to describe this experimental regime, but must be replaced by a more complete frequency-dependent theory of Coulomb interactions.