Saturday, January 25, 2014

Concentration of extended defects in CdZnTe single crystals: Effects of cooling rate after growth

We analyzed two CZT crystals cut from as-grown CdZnTe (CZT) ingots, the only difference between them being the rate of cooling after the crystal growth process. Using White Beam X-ray Diffraction Topography (WBXDT) and Infrared (IR) Transmission Microscopy, we identified and quantified the extended defects, e.g., Te inclusions, dislocations, and sub-grain boundaries. The effects of cooling rate on the size distribution and concentration were studied. The WBXDT and IR images of the fast-cooled crystal revealed very high density of dislocations and sub-grain boundaries, crisscrossing throughout its entire volume, extending from deep inside almost to the surface. In addition, IR analyses showed that the concentration of Te inclusions in the fast-cooled crystal (106 cm−3) was higher than that in the slow-cooled one (105 cm−3). For the latter, both the WBXDT and the IR images were bright and clear with low concentration of defects. We concluded that slow cooling rate can greatly reduce the number of Te inclusions and inclusion-decorated extended defects in as-grown CZT ingots.
Highlights
► We analyze two as-grown CZT single crystals with different cooling rate after growth. 
► We delineate the effects of cooling rate on the distribution of extended defects. 
► The fast-cooled crystal reveals high density of dislocations/sub-grain boundaries. 
► The fast-cooled crystal reveals high concentration of Te inclusions.

Source:Journal of Crystal Growth

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