Investigation of phonons in HgCdTe using Raman scattering and far-infrared reflectivity.

We have measured and analysed the Raman-scattering and far-infrared spectra from unoriented n- and p-type Hg sub 1-x Cd sub x Te with x equal 0.21. Measurements were made in the 80-180 cm high -1 frequency region at temperatures of 10 and 80 K. Comparison of the n- and p-type spectra leads to the conclusion that the electronic contribution to the Raman spectra is small. In particular, the data show that the 135 cm high -1 feature originates in lattice effects and may be related to the Te-3Hg-Cd combination as previously suggested. The weak but distinct fine structure present in the CdTe-like reststrahlen band at about 153 cm high -1 is tentatively assigned to be a result of localised oscillations of Cd ions in the alloy lattice. A study of the spectral changes between 10 and 80 K clearly indicates a softening of the HgTe-like TO phonon.