January 2006 Exclusive Feature: CRYSTAL GROWTH

Using fluid flow simulation to increase yield in crystal growth

By Michael Reed, eV PRODUCTS, a division of II-VI Inc., Saxonburg, Pennsylvania

It is difficult to grow CdZnTe single crystals, and maintaining a high single-crystal yield depends on the design and operation of the high-pressure, electrodynamic gradient furnaces in which the crystals are grown. Running physical experiments in these furnaces is expensive and provides insufficient information about the heat and mass transport in these systems. Using computational fluid dynamics (CFD), the existing furnace operation and solidification process can be modeled and many potential design and process changes can be evaluated. As a result of such efforts, several design changes that have significant improved process yields have been implemented.

Semiconductor single crystals of CdZnTe are important materials for the development of far-infrared, x-ray, and gamma-ray detectors. CdZnTe radiation detectors, first developed in the early 1990s, have the advantages of a large absorption coefficient, compact size, excellent energy resolution, and room temperature operation over other kinds of nuclear radiation detectors. The compound is based on the more widely used material CdTe, but a fraction of the Cd content is replaced with Zn, yielding higher-performance detectors with excellent long-term operational stability.

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Julie MacShane, Managing Editor, SST at email: [email protected].


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