Effect of Doping on the Shift of the Optical Absorption Edge for Circularly Polarized Waves in a Magnetic Field and on the Interband Faraday Rotation in n‐Type GaAs

Abstract

AbstractThe difference of the shift of the optical absorption edge for σ‐ and σ+ polarized waves in a magnetic field is measured on a series of n‐type GaAs samples with various doping levels. The measurements are performed at 77 and 300°K. Following the theory of Luttinger and Kohn[1] the shift of the absorption edge was calculated under the assumption of a broadening of the Landau levels in such a manner as to yield exponential tails with decreasing energy. The assumption of such a broadening is justified since it is known that there are state density tails which extend exponentially decreasing into the gap [2,3]. The effect of doping is considered by applying the Fermi distribution function to the electrons in the Landau levels of the conduction band. The position of the Fermi level and the shape of the absorption edge are determined by absorption measurements. The calculation is in good agreement with the experiment and permits also the explanation of the effect of doping on the interband Faraday rotation near the absorption edge.