Lattice Vibration Spectra of ZnxCd1-xTe Alloys

Reststrahlen reflectivities and localized vibration modes due to light impurities have been measured on Zn x Cd 1- x Te alloys. Each reflection spectrum of these alloys exhibits clear “two-mode” behavior and shows no complex fine structure. Therefore, the theoretical analysis of the spectra can be done relatively easily and simply by developing a modified random-element-isodisplacement model. The localized vibrations of impurities (S, Mg, Be) in Zn x Cd 1- x Te are explained by a model of the charged particles in a static parabolic potential well being affected by the local conditions in the alloy lattice. The constants assumed in the analysis of the reflectivity spectra are consistent with the data in the localized vibrations. Considering these results, a criterion has been proposed to determine whether a certain mixed crystal will exhibit “one-mode” or “two-mode” behavior.