Growth of Cadmium Telluride under Controlled Heat Transfer Conditions.
Final rept. 15 May 82-30 Aug 85,
MASSACHUSETTS INST OF TECH CAMBRIDGE MATERIALS PROCESSING CENTER
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The thrust of this research project was directed at the development of new approaches leading to growth of CdTe single crystals with improved crystalline and chemical perfection. In pursuit of this objective a theoretical analysis was made of the stability of the growth interface as a function of crystallographic orientation. Using the concept of dangling bond densities, it was found that experimentally observed solitary and lamellar twinning phenomena during growth can be directly related to anisotropy in the energetics of unavoidably curved crystal melt interfaces. The theoretical results obtained led to the development of a vertical Bridgman growth configuration in which heat transfer control is accomplished through an axially aligned heat exchange system comprising a heat pipe, a gradient control zone, and a heat levelling device. As an alternate approach to melt growth of CdTe, the suitability of the high pressure liquid encapsulation Czochralski technique HP-LEC was investigated. In the course of this study, analytical techniques, including IR transmission microscopy with image processing and absorption spectroscopy of the optical band edge, were developed and applied to investigations of the bulk defect structure. The results obtained during this research program constitute the basis for extensive DARPA, Air Force, and NASA sponsored research on growth of III-V and II-VI compound semiconductor systems.
- Solid State Physics