Faraday rotation was measured in liquid-phase epitaxial (LPE) Hg, , Cd, Te (x % 0.22) at CO, laser photon energies over the temperature range of 77 K to 300 K for magnetic fields up to 16 kG. We find that t h e Faraday rotation is composed of free-carrier, interband and spin-induced contributions. At 77 K, the interband and spin contributions dominate, resulting in large observed Faraday rotation, i.e. of the order of 10'deg cn-' kG-'. All three contributions are needed to interpret the temperature and magnetic field dependence of the Faraday rotation in our samples. Resonant behaviour observed in the rotation angle is successfully described by impurity-to-band magneto-optical absorption. W e conclude that Faraday rotation could serve as a viable technique for the non-contact measurement of carrier concentration in Hg,,Cd,Te.
Effective mass ratios, m*, of electrons in n-type InSb, GaAs, and near intrinsic and n-type Hgl_xCdxTe for 0.20 < x < 0.30 over the temperature range 77K < T < 296K were measured using Faraday rotation spectroscopy, m* ranged from 0.0186 to 0.0357 for InSb with carrier concentrations, N, in the range 1.76 < N < 110 • 1018 cm ~ at 296K, in good agreement with available values in the literature. Effective masses of HgCdTe were found to be about twice as large at room temperature as band edge effective mass, m*~ calculations. These calculations can be corrected for thermal excitation by adding a factor, m**, to the band edge calculation: m* = m** m*~, where m** was found empirically to be m** = 4.52 • 10-3T + 0.78. The electron's mobility is proportional to the ratio of the electron's Faraday rotation to its absorption; that is, the absorption due to the intraband transitions of the electron itself, not the sample's total absorption, which may include holes, interband transitions, and the like. The constant of proportionality, or the "mobility constant", was measured in n-type GaAs and InSb doped above 18 • 10 ~6 cm -3 using absorption directly. Both HgCdTe and InSb have large intrinsic carrier concentrations, on the order of 101~ cm -3. Hole absorption is the majority component of the sample's absorption at lower n-type dopant concentrations. In these cases, the mobility constant was determined using an absorption cross section.
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