Advances in the crystal growth of semi-insulating CdZnTe for radiation detector applications

The growth of large-volume semi-insulating CdZnTe single crystals with improved structural perfection has been demonstrated by the electrodynamic gradient (EDG) technique and active control of the Cd partial pressure in the ampoule. The EDG furnace nearly completely eliminates the uncontrolled radiative heat transport commonly encountered in traditional Bridgman systems where the charge and furnace move relative to each other. Since the new furnace utilizes electronically controlled high-precision gradient translation, it achieves superior thermal stability throughout the growth. The control of the Cd partial pressure allowed the solidification and cool-down of the ingots close to the stoichiometric composition. As a result, the formation and incorporation of large-size (≥1 μm diameter) Te inclusions was avoided during crystallization and ingots with high structural perfection were achieved. Adequate electrical compensation has been achieved in most of the crystal growth experiments yielding CdZnTe crystals with bulk electrical resistivity in the 10⁹-10¹⁰ Ω·cm range and electron mobility-lifetime product as high as μτ_e=1.2×10^-3 cm²/V. The materials exhibit good spectral performance in the parallel plate detector configuration.