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Vertical Gradient Freezing Using Submerged Heater Growth With Rotation and With Weak Magnetic and Electric Fields
NORTH CAROLINA STATE UNIV AT RALEIGH DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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Investigations for the melt growth gallium-antimonide GaSb semiconductor crystals are underway at the US Air Force Research Laboratory at Hanscom Air Force Base by the vertical gradient freeze VGF method utilizing a submerged heater. Electromagnetic stirring can be induced in the gallium-antimonide melt just above the crystal growth interface by applying a weak radial electric current in the melt together with a weak axial magnetic field. A force convection in the melt can be induced by rotating the heater. This paper uses a Chebyshev spectral collocation method and investigates the effects of heater rotation and electromagnetic stirring on the melt motion during the VGF process using a submerged heater. Clockwise and counterclockwise rotations of the heater augment and opposes the flow induced by the electromagnetic stirring, respectively. The radial velocity along the crystal-melt interface is proportional to both the strength of the electromagnetic stirring and the clockwise rotation of the heater. A relatively low rotation rate in the clockwise direction significantly increases this radial velocity.
APPROVED FOR PUBLIC RELEASE