The Effect of Post-Growth Thermal Annealing on CdZnTe Crystals Grown by Vertical Gradient Freeze Technique

Te inclusions are the primary performance degrading defects in CdZnTe crystals. Because of the unique properties of CdZnTe, it is not possible to eliminate Te inclusions during the growth process. However, annealing process could decrease the concentration of Te inclusions by dissolving or migrating them at elevated temperatures. Annealing under Cd atmosphere could dissolve Te inclusions by introducing new Cd atoms into CdZnTe crystals and compensating excess Te atoms inside of inclusions. However, implemented Cd atoms can form interstitial Cd defects easily; thus, annealing under Te atmosphere is needed to eliminate intestinal Cd defects created by Cd-annealing. In this study, annealing under different atmospheres is studied, and changes in Te inclusion concentrations are observed for various crystals. Additionally, it is observed that the resistivity of doped crystals decreases significantly after Cd-annealing, which is restored with Te-annealing. On the other hand, undoped CdZnTe crystals act differently after annealing steps.