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The study of dopant segregation behavior during the growth of GaAs in microgravityAn investigation into the segregation behavior of selenium doped gallium arsenide during directional solidification in the microgravity environment was conducted using the Crystal Growth Furnace (CGF) aboard the first United States Microgravity Laboratory (USML-1). The two crystals grown were 1.5 cm in diameter and 16.5 cm in length with an initial melt length of 14 cm. Two translation periods were executed, the first at 2.5 microns/s and after a specified time, which was different between the two experiments, the translation rate was doubled to 5.0 microns/s. The translation was then stopped and the remaining sample melt was solidified using a gradient freeze technique in the first sample and a rapid solidification in the second experiment. Measurement of the selenium dopant distribution, using quantitative infrared transmission imaging, indicates that the first sample initially achieved diffusion controlled growth as desired. However, after about 1 cm of growth, the segregation behavior was driven from a diffusion controlled growth regime to a complete mixing regime. Measurements in the second flight sample indicated that the growth was always in a complete mixing regime. In both experiments, voids in the center line of the crystal, indicative of bubble entrapment, were found to correlate with the position in the crystal when the translation rates were doubled.
Document ID
19950007801
Document Type
Conference Paper
Authors
Matthiesen, David H. (Case Western Reserve Univ. Cleveland, OH, United States)
Majewski, J. A. (Case Western Reserve Univ. Cleveland, OH, United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1994
Publication Information
Publication: NASA. Marshall Space Flight Center, Joint Launch + One Year Science Review of USML-1 and USMP-1 with the Microgravity Measurement Group
Subject Category
MATERIALS PROCESSING
Funding Number(s)
CONTRACT_GRANT: NAS8-39695
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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