The refractive index dispersion of Hg_1-xCd_xTe by infrared spectroscopic ellipsometry

The refractive indices of Hg_1-xCd_xTe (x = 0.276, 0.309, and 0.378) bulk samples in the region below, in, and above the fundamental band gap have been measured by infrared spectroscopic ellipsometry at room temperature. A refractive index peak, in which the corresponding energy equals approximately the band gap energy, is observed for each refractive index spectrum with different compositions. Above the band gap, the refractive index drops quickly near the gap, then decreases slowly as photon energy increases. The refractive index n above the band gap is found to follow the Sellmeier dispersion relationship n²(λ) = A + B/λ² + C/λ⁴ + D/λ⁶ as a function of the wavelength of light λ.