Comparative study of dislocation densities in CdZnTe ingots grown with different carbon coatings

Cadmium Zinc Telluride (CdZnTe) is known to be one of the best room temperature X-ray and gamma-ray radiation detector's materials. However, the supply of high-quality CdZnTe detectors is limited due to crystal defects such as dislocations, impurities, Te inclusions that are generated during the crystal growth process. Dislocations are generated due to the stress/strain in the growth process. In this study, we characterized dislocation densities in CdZnTe crystals grown by different techniques (i.e. different carbon-coating thickness and ampoule's shapes) for the suggestion of better growth techniques. Dislocations densities were revealed using a Saucedo solution and analyzed by an infrared microscope. The thick carbon-coated ampoules generated fewer dislocations than the thin carbon-coated ampoule and the ampoule design did not affect the etch pit densities (EPD) as much than carbon-coating thickness. Also, we concluded that a proper crystal growth rate and cooling down rate is one important factor in minimizing dislocations in CdZnTe crystals. The effects of dislocations on the CdZnTe detector's performance was evaluated from the 241Am gamma-response, which fabricated from low and high densities of etch pit region.