It has been established that the Raman scattering (RS) of chalcogenide glass–like semiconductors (CGS) materials
As-Se-S and As-Se-Te at frequencies below 100 cm<sup>-1</sup> consists of two parts: first - which the intensity with increasing
frequency up to 30 ÷ 40 cm<sup>-1 </sup>decreases (quasi-elastic scattering); second - which have been observed a broad band with a
maximum at frequencies of ~ 63 ÷ 67 cm-1 (boson peak - BP). Such a case is absent in the respective crystals. The observed
features are associated with relaxation and excess density of states of acoustic vibrations in irregularities is localized with
nanometer-size of material. It is shown that the contribution of the different types of scattering in a low-frequency range
depends on the degree of disorder in the material, which varies with the change of chemical composition and by doping.