The influence of a traveling magnetic field (TMF) on vertical gradient freeze (VGF) growth of cadmium zinc telluride (CZT) is studied using a coupled model of magnetic induction, fluid dynamics, and heat transfer. Simulations are performed to determine the influences of current, phase shift, and frequency on melt flow and growth interface shape. A downward traveling electromagnetic wave drives flow downward at the wall, which tends to flatten the interface, whereas an upward traveling wave has the opposite effect. An optimum phase shift that maximizes Lorentz force is found to depend only on system geometry. Large currents (∼ 300 A) and high frequencies (∼ 500 Hz) make a significant impact on interface shape in the absence of thermal buoyancy, but are ineffectual under realistic conditions in a 4 in.-diameter ampoule, for which buoyancy dominates Lorentz force throughout the melt. The results indicate that interface shape in this CZT growth system is strongly governed by furnace heat transfer and is difficult to modify by TMF-driven forced convection.
Bibliographical noteFunding Information:
This material is based upon work supported in part by the Department of Energy, National Nuclear Security Administration , under Award DE-FG52-08NA28768 , the content of which does not necessarily reflect the position or policy of the United States Government, and no official endorsement should be inferred. Computational resources were provided by the Minnesota Supercomputing Institute. The authors would like to thank Gaurab Samanta for his preliminary work on this project and Peter Rudolph for suggesting study of the double-frequency approach to TMF.
- A1. Computer simulation
- A1. Convection
- A1. Heat transfer
- A1. Magnetic fields
- A2. Gradient freeze technique
- B2. Semiconducting II-VI materials