Influence of dynamic temperature adjustments during growth on the material properties of CZT radiation devices

There are several challenges in producing detector grade material based on Cadmium Zinc Telluride (CZT), which include material synthesis and growth of electrically compensated crystals as well as the extraction of high resistivity material suitable for device applications. One of the challenges towards producing large volumes of compensated material using the Vertical Gradient Freeze (VGF) method is the axial and radial variations in material homogeneity. Growth induced strain is one of the most important factors in the crystal growth of CZT because of the low critically resolved shear stress (CRSS) value for this material. In this work, methods to reduce the thermo-mechanical stress imparted into the crystal have been implemented. Specifically, crystals have been grown under dynamic temperature gradients to minimize the temperature gradient across the ingot, while maintaining relatively higher temperature gradients at the Solid Liquid Interface (SLI). How this adjustment affects bulk resistivity and photoconductivity has been investigated.

► CdZnTe crystals grown using VGF method, using dynamic temperature gradients.
► This modified VGF method is intended to reduce the thermo-mechanical stress.
► Investigate how fluctuations in temperature affect as-grown crystals.
► Investigate devices harvested along the axial direction.
► CZT devices studied using PICTS, I–V, IR-Transmission and gamma spectroscopy.