Infrared Absorption and Its Sources of CdZnTe at Cryogenic Temperature

To reveal the causes of infrared absorption in the wavelength region between electronic and lattice absorptions, we measured the temperature dependence of the absorption coefficient of p-type low-resistivity ($$\sim 10^2~ \Omega \mathrm{cm}$$ ∼ 10 2 Ω cm ) CdZnTe crystals. We measured the absorption coefficients of CdZnTe crystals in four wavelength bands ($$\lambda =6.45$$ λ = 6.45 , 10.6, 11.6, 15.1$$~\mu $$ μ m) over the temperature range of $$T=8.6$$ T = 8.6 -300 K with an originally developed system. The CdZnTe absorption coefficient was measured to be $$\alpha =0.3$$ α = 0.3 -0.5 $$\mathrm{cm}^{-1}$$ cm - 1 at $$T=300$$ T = 300 K and $$\alpha =0.4$$ α = 0.4 -0.9 $$\mathrm{cm}^{-1}$$ cm - 1 at $$T=8.6$$ T = 8.6 K in the investigated wavelength range. With an absorption model based on transitions of free holes and holes trapped at an acceptor level, we conclude that the absorption due to free holes at $$T=150$$ T = 150 -300 K and that due to trapped-holes at $$T<50$$ T < 50 K are dominant absorption causes in CdZnTe. We also discuss a method to predict the CdZnTe absorption coefficient at cryogenic temperature based on the room-temperature resistivity.

Two-time Calibration at Both Ends for Sulfur Measurement by Using High Frequency Induction Infrared Absorption Method

High frequency induction heating infrared absorption method is a relative measurement method, and it requires calibrating the analyzer during the measurement process. Usually, one-time calibration on an analyzer is made for high sulfur value by using standard substances. The method proposed by this paper calibrates carbon-sulfur analyzers with a method of two-time calibration at both ends, which eliminates the impact of sulfur blank and thus improves the accuracy and precision of ultra-low sulfur measurement. The method extents the lower limit of measurement of sulfur in high temperature alloy, to 0.00005%, namely, 0.5ppm.