Thermal stress simulation and CdZnTe crystal growth by low pressure bridgman method

Finite elements method was used to numerically simulate the thermal stress distribution in CdZnTe Crystal at the site where the crystallization just finished. The simulation results showed that the thermal stresses near the quartz ampoule wall, in the part of changing-diameter and at the tip on the crystal were higher, with orders of about 108 N/m2, but exhibited homogenous distribution in middle part of crystal, with orders of about 10 N/m. To prevent the dislocation in the part of changing-diameter and the tip end of the head part elongating into the middle part, a new kind of process was put forward by using different descent rates in the different stage of crystal growth and a melt-back process when the crystal descended down to the part of changing-diameter. The experimental results showed that the dislocation density in CdZnTe crystal grown by the new process decreased much to a very low level of 2 × 102 cm-2, and the utilization ratio of crystal greatly increased if compared to the as-grown crystal by high press Bridgman method.