Airplane and Drop Experiments on Crystallization of In x Ga 1-x Sb Semiconductor under Different Gravity Conditions
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Airplane and Drop Experiments on Crystallization of InxGa1-xSb Semiconductor under Different Gravity Conditions Krishnan Balakrishnan1, Yasuhiro Hayakawa1, Hideki Komatsu1, Noriaki Murakami1, Tetsuo Nakamura1, Tadashi Kimura1, Tetsuo Ozawa2, Yasunori Okano3, Masafumi Miyazawa3, Sadik Dost4, Le. H. Dao5 and Masashi Kumagawa1 1 Research Institute of Electronics, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8011, Japan. 2 Dept. of Electrical Eng., Shizuoka Inst. of Sci. & Tech., Fukuroi 437-8555, Japan. 3 Faculty of Eng., Shizuoka University, Hamamatsu 432-8561, Japan. 4 Dept. of Mech. Eng., University of Victoria, Victoria, BC, Canada V8W 3P6. 5 Adv. Mat. Res. Lab., Univ. du Quebec, INRS, Verennes, Qubec, Canada J3XIS2. ABSTRACT Melting and crystallization experiments of InGaSb were done under the reduced gravity condition (10-2G) in an airplane and at the normal gravity condition (1G) in the laboratory. Crystallized InGaSb was found to contain many needle crystals in both the cases. Reduced gravity condition was found to be more conducive for crystal growth than the normal gravity condition. Formation of spherical projections on the surface of InGaSb during its crystallization was in-situ observed using a high speed CCD camera in the drop experiment. Spherical projections showed dependence of gravity during its growth. Indium compositions in the spherical projections were found to vary depending on the temperature. INTRODUCTION InxGa1-xSb is a potential optoelectronic device oriented material and it could be used to fabricate commercially viable detectors, thermo-photo-voltaic (TPV) cells. InxGa1-xSb along with its binary counterparts GaSb and InSb are interesting III-V model materials for space ventures because of their low melting temperatures (712˚C and below) and low vapour pressures. It is extremely difficult to grow high quality InxGa1-xSb bulk crystals on earth due to gravity induced effects. As the densities of the components are different, solute transport occurs due to buoyancy. For this reason, microgravity condition in space is ideally suited to grow high quality and defect free InxGa1-xSb crystals as the gravity induced negative effects can be overcome [1-3]. In order to investigate the effect of gravity on the dissolution and crystallization processes, we carried out two microgravity experiments. The first one was performed in the Second International Microgravity Laboratory (IML-2) in 1994 [4-7]. We studied the effects of diffusion and convection on the melt mixing of In/GaSb/Sb. One of the important observations made in this venture was the formation of many circular projections on the surface of the InGaSb spherical sample. The indium compositions in this area were different from those in the main body of the sample. The other experiment was carried out in a Chinese recoverable satellite in 1996 [8-10]. It is not always possible to venture microgravity experiments in space using space shuttles due to economic and other major constraints. Hence, it is necessary to find alternate avenues
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