Compositional uniformity of a Si0.5Ge0.5 crystal grown on board the International Space Station

Publication date: 1 June 2015
Source:Journal of Crystal Growth, Volume 419
Author(s): K. Kinoshita , Y. Arai , Y. Inatomi , T. Tsukada , H. Miyata , R. Tanaka , J. Yoshikawa , T. Kihara , H. Tomioka , H. Shibayama , Y. Kubota , Y. Warashina , Y. Ishizuka , Y. Harada , S. Wada , T. Ito , N. Nagai , K. Abe , S. Sumioka , M. Takayanagi , S. Yoda
A Si0.5Ge0.5 crystal was grown on board the International Space Station (ISS) using the traveling liquidus-zone method. Average Ge concentration was 49±2at% for the growth length of 14.5mm. Radial compositional uniformity was excellent especially between the growth length of 3 and 9mm; concentration fluctuation was less than 1at%. In this experiment, cartridge surface temperatures were monitored and heater temperatures were adjusted based on the monitored temperatures for improving compositional uniformity of a grown crystal. A step temperature change by 1°C was imposed for adjusting heater temperatures. This procedure made it possible to observe growth interface shape; striations due to heater temperature change were observed by a backscattered electron image. Growth rates were precisely determined by the relation between interval of heater temperature change and the distance between striations. Based on the measured growth rates, two-dimensional growth model for the traveling liquidus-zone method was discussed.