Optical phonons inCd1−xZnxTe

We have combined infrared and Raman methods to study the transverse- and longitudinal-optical (TO and LO) phonons in bulk ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Zn}}_{\mathit{x}}$Te (x=0.005–1), for the first time at temperatures as low as 20 K. The samples were grown by the two-zone Bridgman method. We confirm that, within a two-mode model, both the CdTe- and ZnTe-like TO-mode frequencies increase with x, unlike any other II-VI ternary compound with known phonon modes, and unlike a recent report for ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Zn}}_{\mathit{x}}$Te films grown on GaAs by molecular-beam epitaxy. The ZnTe-like TO frequency at very low x is near the prediction from impurity-mode theory. The infrared spectra show signs of clustering behavior like that seen in ${\mathrm{Hg}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Cd}}_{\mathit{x}}$Te.