Temperature Dependence of the Vibrational Mode of Pb 1 – x Sn x Te Films Grown by MBE on the GaAs/CdTe Hybrid Substrate

Reflectance spectra of thin Pb 1 – x Sn x Te films (~60 nm) with x = 0.25, 0.53, and 0.59, grown by MBE on hybrid GaAs/CdTe substrates, are measured in the frequency range of 20–5500 cm –1 and the temperature range of 5–300 K. The temperature dependence of transverse optical phonon frequencies and structural phase transition temperatures are determined based on a dispersion analysis. An increase in the plasma frequency with decreasing temperature in the range 300‒77 K in all films is detected.