IR images reveal that Te inclusions exist in CdZnTe crystal in the form of square, hexagonal and triangular shapes. The density of Te inclusions for sizes above 5 μm sharply varied from 2.27 × 103 cm−2 to 4.52 × 105 cm−2 with a consequent reduction in IR transmittance from ∼60.5% to ∼55% when the Te-rich volume increased to 83 ppma. Raman spectra suggested that the origin of a new peak at 262.5 cm−1 could be a secondary phonon with A1 symmetry and E symmetry of Te inclusions. The peaks of triangular Te inclusions in Te-rich CdZnTe wafers were shifted to high energy, suggesting that compressive stress existed around the Te inclusions.
Fig. 1. Raman scattering spectra of CZT crystals grown under different Te-rich volume conditions.