Study on crystalline of Cd-annealing CdZnTe wafers grown by Bridgman method

The room temperature infrared transmission spectra, infrared microscope and X-ray double-crystal rocking curve measurement were used to characterize the annealing effect of CdZnTe crystal wafers. Cd-annealing of Bridgman grown CdZnTe wafers for 5h or longer time at 700°C enhances the IR transmittance of the wafer up to 64% and decreases Te precipitate density. The high IR transmittance obtained is attributed to annihilation of Cd vacancies or elimination of Te precipitates during annealing in Cd vapor. It is also found that Cd anneal degrades the CdZnTe crystalline quality. The damage depth is 50-130μm. The two mechanism of crystalline quality damage for an annealing in Cd vapor are possible (i) depletion of Zn from CdZnTe surface, and (ii) impurities released from the Te precipitates resulted in regrowth of CdZnTe give rise to imperfect crystallinity. However, the impurities released from the Te precipitates to CdZnTe wafer surface during Cd-annealing can be cleaned by removing the damaged surface of CdZnTe wafers, and therefore the CdZnTe wafers as substrates are more beneficial to growing Hg_1-xCd_xTe epilayers.