Studies on the deep-level defects in CdZnTe crystals grown by travelling heater method

The variation of deep level defects along the axis of CZT:In ingots grown by Travelling Heater Method was investigated by the means of thermally stimulated current (TSC) spectra. Models for the reaction among different defects In, Te_i, and V_Cd were used to analyze the variation of deep level defects along the growth direction. It was found that the density of In dopant-related defects is lower in the tip, but those of Te antisites and Te interstitials are higher in the tip. The density of cadmium vacancy exhibits an initial increase followed by a decrease from the tip to tail of the ingot. In PL spectra, the intensities of (D₀, X), (DAP) and D_complex peaks obviously increase from the tip to the tail, due to the increase of the density of In dopant-related defects (In_cd ⁺), Cd vacancies, and impurities. The low concentration of net free holes was found by Hall measurements, and high resistivity with p-type conduction was demonstrated from I–V analysis. The mobility for electrons was found to increase significantly from 634 ± 26 cm²V⁻¹s⁻¹ in the tip to 860 ± 10 cm²V⁻¹s⁻¹ in the tail, due to the decrease of the deep level defect densities.