Far-infrared study of alloying in the HgTe-CdTe superlattice

The far-infrared reflectivity spectra of three HgTe-CdTe superlattices from two sources [HgTe/CdTe thicknesses (Å/Å): 64/26, 7/35, 32/57] have been measured at 300, 77, and 6 K. Analysis of transverse optical phonon structure between 80 and 180 cm^-1 with different alloying models shows that the first of these superlattices contains HgTe and CdTe with no evidence of significant mixing, whereas the others contain HgTe and homogeneous Hg_1-xCd_xTe. An earlier study of the HgTe-CdTe band gap also indicated homogeneous alloying. The reflectivity data were analyzed with a superlattice dielectric function which is shown to be valid in the far infrared.