Large-grain SiGe-on-insulator with uniform Si concentration by segregation-free rapid-melting growth

• Published in: Applied physics letters 2014-09, Vol.105 (10)
• Main Authors: Matsumura, Ryo, Kato, Ryusuke, Sadoh, Taizoh, Miyao, Masanobu
• Format: Article
• Language: English
• Subjects: Applied physics; Cooling; Cooling rate; Crystal growth; Heat treating; Nucleation; Semiconductor devices; Silicon germanides; Silicon substrates; Solidification; Thin film transistors
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4895512

Large-grain SiGe-crystal-on-insulator is essential for fabrication of devices such as advanced thin film transistors and/or photosensors. For these purposes, rapid-melting growth of amorphous SiGe stripes (7%–20% Si concentration) on insulating substrates is investigated over a wide range of cooling rates (from 2 to 17 °C/s). The growth features of SiGe change dynamically, depending on the cooling rate. A low cooling rate produces large crystals with laterally graded Si concentration profiles caused by significant Si segregation during solidification. In contrast, a high cooling rate suppresses the Si segregation, but small grains form because of high spontaneous nucleation under super-cooling conditions. By tuning of the cooling rate, moderate super-cooling conditions are obtained as a function of the Si concentration. This controls both the Si segregation and the spontaneous nucleation, and produces large SiGe crystals (∼400 μm length, 7%–20% Si concentration) with three-dimensionally uniform Si profiles.