Study of the diffusion of Te inclusions in CdZnTe nuclear detectors in post-growth annealing

Despite immense endeavor invested in optimizing the crystal growth parameters and the post growth improvement methodologies proposed by numerous studies, there are still unresolved shortcomings of CdZnTe crystals to produce commercial-grade CdZnTe detectors. Post-growth thermal annealing under Zn, Te, or Cd vapor overpressure at various temperature have been the approach attempted to improve the crystallinity of CdZnTe crystals. This paper presents results of post growth annealing of CdZnTe detectors that shows both reduction in the sizes of Te inclusions and the migration of the inclusions towards the high-temperature side of the crystal. Two set of annealing experiments were made. The first is annealing under Cd vapor overpressure in vacuum at 600 °C for 45 minutes at a temperature gradient of 10 °C/cm. The second set of CdZnTe post-growth annealing experiments was carried out at 700 °C CdZnTe annealing temperature with the Cadmium temperature at 650 °C, 30 minutes annealing time, and temperature gradient of 10 °C/cm. The reduction in the sizes of Te inclusions ranges from 8% to 38%.