RAMAN STUDIES OF CRYSTAL PERFECTION IN MERCURY CADMIUM TELLURIDE WAFERS

Resonant second-order Raman scattering of zone-center longitudinal-optical phonons [2LO(Γ)] in Hg0.8Cd0.2Te and Hg 0.7Cd0.3Te is reported. Three 2LO(Γ) components are seen, which are assigned as LO1+LO1, LO 1+LO2 and LO2+LO2 combinations (where 1 denotes CdTe-like and 2 denotes HgTe-like). The intensity of these bands is very sensitive to crystal damage, making this a very useful probe of near-surface crystal order. The detection of Te inclusions by Raman microscopy is reported and a variation in peak position is attributed to different inclusions being under varying tensile strain. Bromine-methanol etching of Hg1-xCdxTe is shown to lead to a buildup of Te on the surface, while an increase in intensity of the 2LO(Γ) modes of the Hg 1-xCdxTe reflects removal of surface damage.