Investigation of Seeded Vertical Gradient Freeze (VGF) Growth of CdZnTe Bulk Crystals

• Cylindrical CdZnTe seeds were obtained using a CNC drilling system with custom tooling. • Complete seed melting issue was explored using heat shields near seed well region. • Using a previously grown single crystal seed, seeded VGF growth of CdZnTe was conducted. • Seeding and grain evolution of the grown CdZnTe ingot were investigated. Due to the requirement for superheating above the melting point in the homogenization process of CdZnTe material, complete seed melting remains as a significant problem for the seeded vertical gradient freeze (VGF) growth of CdZnTe. In addition, due to the typical low single crystal yields in VGF growth of CdZnTe, obtaining single crystal seed material with desired geometries could be considered as a challenge. In this study, single crystal CdZnTe seeds of cylindrical geometry with 10 mm diameter and up to 30 mm length were successfully obtained using a Computer Numerical Control (CNC) cutting system. Moreover, to avoid complete seed melting, a novel design of the growth crucible and support system along with radiation shielding around seed region is employed. Temperature profiling and growth experiments were conducted to observe seed melting and seeded crystal growth of CdZnTe. Initial results of a seeded VGF growth using a single crystal CdZnTe seed is reported.