Raman scattering in Hg0.8Cd0.2Te

Abstract
We report the first polarization dependent Raman scattering study in Hg0.8Cd0.2Te from the (100) and (111) faces. The Raman spectra were recorded in the back scattering geometry at 77 K using several lines of an Ar+ laser near resonance with the E1 optical gap. The study leads to an unambiguous identification of the HgTe and CdTe-like transverse optical (TO) and longitudinal optical (LO) phonon features. The HgTe-like TO and LO phonons occur at 122±1 cm−1 and 140±1 cm−1 and the CdTe-like LO phonon occurs at 156±1 cm−1; the CdTe-like TO–LO splitting was too small to be observable. The presence of a symmetry forbidden HgTe-like TO phonon from the (100) face indicates the presence of defects or disorder. A defect mode was observed at ∼108 cm−1. In addition, an extremely surface sensitive feature was seen at 132 cm−1 and has been tentatively assigned to a coupled LO phonon–intersubband excitation from the natural occurring surface inversion layer. A strong feature observed at 135 cm−1 may arise from clustering effects.