Effect of Marangoni Convection on InSb Single Crystal Growth by Horizontal Bridgman Method
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Effect of Marangoni Convection on InSb Single Crystal Growth by Horizontal Bridgman Method K. Kodera1, A. Kinoshita1, K. Arafune 2, Y. Nakae1, and A. Hirata1 1 Department of Chemical Engineering, Waseda University, Okubo 3-4-1, Shinjuku-ku, Tokyo, 169-8555, Japan 2 Research Institute of Electronics, Shizuoka Univ., Hamamatsu, Shizuoka 432, JAPAN ABSTRACT It is necessary to clarify the effect of Marangoni convection on single crystal growth from a melt in order to improve the quality of the grown crystal. Particularly, the deviation of crystalmelt (C-M) interface from a planar shape is a major problem because it may deteriorate the quality of the grown crystal. In this paper, we investigated the effect of thermal and solutal Marangoni convection on C-M interface shape in an In-Sb binary system by the horizontal Bridgman (HB) method. The C-M interface concavity strongly depends on the cooling rate and the temperature gradient under uniform concentration distribution conditions in the melt. A large concavity was observed at low cooling rates and high temperature gradient conditions. The concavity was found to be caused by thermal Marangoni convection, by taking Péclet number into account. Then, we varied the composition of the In-Sb binary system to induce solutal Marangoni convection intentionally. The C-M interface was kept planar in case solutal Marangoni convection occurred in the direction opposite to the thermal one. Therefore, we believe that the utilization of solutal Marangoni convection will be a new control technique to make the C-M interface planar for the HB system. From these results, it was clarified that Marangoni convection plays a significant role in the HB crystal growth system. INTRODUCTION At present, most of the semiconductor bulk crystals are grown by melt growth methods such as the Czochralski (CZ) or the horizontal Bridgman (HB) method. During crystal growth by these methods, convection in melt affects the quality of the grown crystals. Therefore, it is necessary to clarify the mechanism of convection in melt and to control the convection to improve the quality of the crystal. The convection can be divided into buoyancy convection and Marangoni convection. The driving force of the former is the buoyancy difference in the melt, and that of the latter is the surface tension difference on the free surface. The convection can also be divided into thermal and solutal convection because those driving forces vary with temperature and concentration. Particularly, thermal buoyancy convection has been extensively investigated since as early as the beginning of the 20th century [1]. On the other hand, the importance of Marangoni convection, which has nothing to do with gravity, was recognized after semiconductor crystal growth experiments were conducted under microgravity conditions in the 1980s [2]. Since then, Marangoni convection has been investigated by many researchers [3,4]. Regarding solutal convection, although solutal buoyancy convection has been studied as a double diffusive problem, solutal Mar
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