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Proceedings Paper

The effect of stable menisci shapes on the zinc distribution in CdZnTe crystals grown by dewetted Bridgman technique
Author(s): Liliana Braescu
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Paper Abstract

The unusual thermophysical properties of the CdZnTe crystals (high melt viscosity, a large latent heat of fusion, fairly large equilibrium segregation coefficient, etc.) cause considerable difficulty in maintaining uniform zinc composition in the grown crystal. The disadvantages can be overcome by the dewetted Bridgman technique in which the crystal is grown detached from the ampoule wall by a liquid free surface at the level of the solid-liquid interface, called liquid meniscus, which creates a gap between the grown crystal and the ampoule wall that bring together low contact stress with low thermal stress. Crystal growth experiments showed that, in some conditions, chemical impurities at the liquid surface may lead to unintended contamination that can increase the wetting angle artificially. This high sensitivity of the wetting angle changes the meniscus shape, and hence the dopant distribution in the grown crystal. For evaluating numerically the effect of the menisci shapes on the Zn distribution in CdZnTe crystals grown by dewetted Bridgman technique, a pseudo quasi-steady state model is considered in the framework of a 2D axisymmetric geometry containing two types of stable menisci: (i) a "S" shape meniscus that corresponds to the sum-of-the-angles criterion αe+θc<180° (αe is growth angle and θc is wetting angle); (ii) a globally convex meniscus that corresponds to chemical contamination, i.e., αe+θc>180°. Numerical computations including incompressible fluid flow in the Boussinesq approximation, heat and mass transfer, and Marangoni effect, are performed using finite element technique. It is proven that a convex meniscus assures the best impurity distribution.

Paper Details

Date Published: 17 September 2011
PDF: 9 pages
Proc. SPIE 8120, Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications V, 81200E (17 September 2011); doi: 10.1117/12.893236
Show Author Affiliations
Liliana Braescu, EMT-INRS (Canada)
Univ. de Vest din Timisoara (Romania)


Published in SPIE Proceedings Vol. 8120:
Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications V
Shizhuo Yin; Ruyan Guo, Editor(s)

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