Faraday Rotation inp-Type Semiconductors

Faraday rotation has been investigated for $p$-type germanium, gallium arsenide, gallium antimonide, indium arsenide, and zinc telluride from the neighborhood of intrinsic absorption edge up to 20 μ. The spectra show maxima and minima resulting from electron transitions between various sets of Landau levels which are associated with the two degenerate hole bands and the spin-orbit band. Transitions between levels in the same sets correspond to the free-carrier effect of a simple energy band, giving a rotation proportional to ${\lambda }^2$. Transitions between the levels of the spin-orbit band and those of the two hole bands produce a structure in the rotation spectrum which is observed in the case of Ge and GaAs, where the spin-orbit splitting is smaller than the energy gap. At long wavelengths, transitions between levels associated with different hole bands are important. In ZnTe, a different spectrum is observed at low temperature, which is produced by holes bound to impurities. The dependence of Faraday rotation on carrier relaxation time has been studied for germanium. The magnitude of rotation is found to decrease with decreasing relaxation time. Theoretical calculations are made for germanium. Satisfactory agreement with the experimental data is obtained.