(711h) Melt Growth of CZT with Convex Interfaces VIA A Bell-Curve Gradient Freeze Profile

The availability of large, single crystals of cadmium zinc telluride (CZT) with uniform properties is key to improving the performance of gamma radiation detectors.  The quality and cost of CZT substrate is primarily determined by crystal growth outcomes.  However, the growth of these crystals is still not well understood, and most modifications to crystal growth have been driven by intuition obtained from growth experience with traditional semiconductor systems that are very differently from CZT. We aim to advance the practice of crystal growth by applying physics-based, computational models to understand the most important factors affecting these processes. 

In this presentation, a novel, bell-curve furnace temperature profile is presented and predicted to achieve macroscopically convex solid-liquid interface shapes during melt growth of CZT in an electrodynamic gradient freeze (EDG) furnace.  A strategy is also presented to dynamically adapt this furnace profile so that uniform, convex interface shapes are maintained through an entire CZT growth run.  This approach represents a significant advance over traditional gradient-freeze profiles, which always result in concave interface shapes, and furnace heat transfer modifications, such as redesigned ampule support pedestals, that can achieve convex interfaces, but only over only a small portion of the growth run.

Realizing a convex solidification interface via this adaptive bell-curve furnace profile is postulated to result in better crystallinity and higher yields than conventional CZT growth techniques.  Importantly, this strategy may be applied to any Bridgman configuration that utilizes multiple, controllable heating zones.