Refractive index enhancement effect in Hg1-xCdxTe near the fundamental gap

The refractive indices of Hg1-xCdxTe bulk samples with the composition x = 0.276, 0.309, and 0.378 were measured by infrared spectroscopic ellipsometr y at room iemperature in the energy regions which were below, across, and a bove the fundamental band gap. An obvious refractive index enhancement effe ct was observed in the refractive index spectra for each composition. The e nergy position of the maximal refractive index value equals approximately t hat of the band gap. The refractive index versus wavelength lambda above th e band gap for xbetween x = 0.276 and 0.378 was modeled using a Sellmeier d ispersion relationship n(2)(lambda)= a(1)+a(2)/lambda (2)+a(3)/lambda (4)+a (4)/lambda (6).