Visible and Ultraviolet Reflectivity of Hg_0.8Cd_0.2Te

The fundamental reflectivity spectra of Hg_0.8Cd_0.2Te have been investigated. The feature of the spectra is the presence of E_l and E₂ peaks within the fundamental absorption region. A three dimensional saddle point is used to fit the E_l and E_l+ Δ_l critical point and some simulated calculation is done for E₂ at X point. The measured and calculated reflectivities are compared and prominent features of the reflectivity spectra are identified with critical point transition at the and X points in the Brillouin zone.