Bulk crystal growth process for compositionally homogeneous gallium indium antimonide substrates
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Authors
Kim, Hee Jeong
Issue Date
2005-08
Type
Electronic thesis
Thesis
Thesis
Language
ENG
Keywords
computer , Systems engineering , Electrical
Alternative Title
Abstract
The roles of forced and natural convections III the liquid on the radial alloy distribution in vertical Bridgman growth Ga₁₋ₓInₓSb bulk polycrystals (20-50 mm diameter) have been investigated. The shape of the solid-liquid interface has been found to be highly curved under growth conditions necessary for preventing constitutional supercooling such as high axial temperature gradients and low growth rates. Lowering the axial temperature gradient does flatten the interface shape, but extremely slow growth rate (below 0.1 mm/hr) is necessary for avoiding constitutional supercooling. Forced convection induced by melt mixing strategies developed in this work efficiently accelerates the dispersion of the excess solute from the growth interface into the entire melt volume thus leading to a 4-5 fold increase in the growth rate without constitutional supercooling. This also helps to eliminate micro-cracks in the crystals. A comparative study of various melt stirring schemes with different axial temperature gradients and the resulting alloy distribution in the crystals has been presented in this thesis. A combination of axial thermal gradient of approximately 15 °C/cm, accelerated crucible rotation (ACRT) with maximum crucible acceleration up to 100 rpm in 60 seconds and growth rate in the range of 0.2-0.5 mmIhr has been found to be most suitable for radially homogeneous Ga₁₋ₓInₓSb crystals. Bulk polycrystals of 50 mm diameter Ga₁₋ₓInₓSb across the entire composition range (x = 0 - 1) has been successfully grown under these conditions.
Description
August 2005
School of Engineering
School of Engineering
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY