Optical characterization of Hg_{1 - x}Zn_xTe crystals grown by the travelling heater method

Optical studies, including electrolyte electro-reflectance (EER) and FT-IR, have been used to characterize Hg_{1 - x}Zn_xTe (MZT) crystals grown by the travelling heater method (THM). The results of EER spectra proved that the crystalline quality of ingots was quite good and its alloy composition was uniform within a grain. The temperature dependence of the energy band gap of the crystals was determined from the FT-IR experiments. The values of d(E_g) dT could be considered to be constant for various alloy compositions, and the relation between them can be fitted by an analytical expression: d(E_g) dT = (5.948 - 16.53x + 5.211x²) × 10^-4 eV K^-1. However, the E_g values may not be a true linear function of temperature. The deviations from linearity were too small to be unambiguously included in the above expression, except for the critical point, x = 0.392, at which d(E_g) dT = 0 only at higher temperatures and definitely revealed positive values of ≈10^-5 eV K^-1 below 60 K.