Ternary telluride alloys of Ge–Se(Sb)–Te and Si–Ge(Ga)–Te systems are synthesized in glassy and crystalline states for use in the terahertz frequency range. The transmission spectra of the obtained alloys are measured and studied in a wide wavelength range from 0.75 to 300 μm. The possible mechanisms of their formation are discussed. A comparative analysis of the results shows that the Ge14Sb28Te56 alloy of the GST system is most promising. Its phonon spectrum is in the range of 40– 280 cm–1, limiting the long-wavelength transmission window of this alloy by 35 μm. Optimization of the Ge14Sb28Te56 composition, the removal of impurities, and heat treatment will promote a further decrease in the absorbance in the far-infrared spectrum of this alloy.
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