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Proceedings Paper

Physical vapor transport of ZnSe--modeling studies: current status and future course
Author(s): Narayanan Ramachandran
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Paper Abstract

Bulk growth of wide band gap II-VI semiconductors by physical vapor transport (PVT) has been developed and refined over the past several years at NASA Marshall Space Flight Center. Results from a modeling study of PVT crystal growth of ZnSe are reported in this paper. The PVT process is numerically investigate using a 2D formulation of the governing equations and associated boundary conditions. Both the incompressible Boussinesq approximation and a compressible model are tested to determine the influence of gravity on the process and to discern the differences between the two approaches. The influence of a residual gas in included in the models. The results show that both the incompressible and compressible approximations provide comparable results and the presence of a residual gas tends to measurably reduce the mass flux in the system. Detailed flow, thermal and concentration profiles are provided. The simulations show that the Stefan flux dominates the system flow field and the subtle gravitational effects can be gauged by subtracting this flux from the calculations. Shear flows, due to solutal buoyancy, of the order of 50 micron/s for the horizontal growth orientation and 10 micron/s for the vertical orientation are predicted. Whether these flows can fully account for the observed gravity related growth morphological effects and inhomogeneous solute and dopant distributions is a matter of conjecture. A template for future modeling efforts in this area is suggested which incorporates a mathematical approach to the tracking of the growth front based on energy of formation concepts.

Paper Details

Date Published: 6 July 1999
PDF: 12 pages
Proc. SPIE 3792, Materials Research in Low Gravity II, (6 July 1999); doi: 10.1117/12.351297
Show Author Affiliations
Narayanan Ramachandran, Universities' Space Research Association/NASA Marshall Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 3792:
Materials Research in Low Gravity II
Narayanan Ramachandran, Editor(s)

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