Compositional Variations of the Nonresonant Interband Faraday Rotation in Cd_xHg_1‐xTe Single Crystals

Abstract

EYA possibility to change the wavelength of the peak photoconductivity response in Cd,Hgl -xTe (CMT) crystals within a broad spectral interval by means of alloy composition is widely used in fabrication of CMT infrared detectors. The dependence of the optical gap E on the alloy compositional parameter x and temperature T has been determined within a broad range of x values by optical absorption /1, 2/, photoconductivity /3/, and magnetoreflectance /4/. In this note we present results of interband Faraday rotation (FR) measurements at room and liquid nitrogen temperature on samples in the composition range 0.26 -I x 5 0.56. We obtain the energy gap E (x, T) as a function of x and T from comparison of the experimental results with appropriate theoretical calculations. g g Our CMT single crystals were grown in the Institute of Physics, Charles University, by a modified Bridgman method. The as-grown samples (p-types) were mechanically ground and polished to form thin plates with thickness from 50 to 500 Am. The alloy composition was determined by electron beam microprobe. F R was measured by a single beam method with polarizer oriented at an fixed angle 45' with respect to the analyzer. The rotation was calculated from the change of the transmitted beam intensity due to commutation of the external magnetic field 1 T . The infrared radiation was detected either by a PbS o r by a Golay cell and lock-in amplifier. The results were not corrected for multiple internal reflections in the sample.To our knowledge, Faraday rotation on CMT samples has been reported in the narrow spectral region covered by C02 laser lines near 1 0 p m only /5/.Different signs of F R in p-and n-type samples were observed in this spectral region.1) Ke Karlovu 5 , 121 16 Praha 2, Czechoslovakia.