SiGe quantum dot molecules grown on patterned Si (001) substrates

• Published in: Journal of applied physics 2008-08, Vol.104 (4), p.044303-044303-6
• Main Authors: Yang, Hongbin, Zhang, Xiang-jiu, Jiang, Zuiming, Yang, Xinju, Fan, Yongliang
• Format: Article
• Language: English
• Subjects: CRYSTAL GROWTH; GERMANIUM ALLOYS; GERMANIUM SILICIDES; MATERIALS SCIENCE; MOLECULAR BEAM EPITAXY; QUANTUM DOTS; SEMICONDUCTOR MATERIALS; SILICON ALLOYS; STRESS RELAXATION; SUBSTRATES; THIN FILMS
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2968946

SiGe quantum dot molecules (QDMs) grown on patterned Si (001) substrates by molecular beam epitaxy were studied. Experimental results showed that the density, the dimension, and the dimension distribution of the SiGe QDMs grown in the windows were dependent on the window size. When the thickness of the Si 0.8 Ge 0.2 film was 40 nm, QDMs only appeared in the unpatterned areas of the Si substrate and none could be found inside the windows of 6 × 6   μ m 2 on the same substrate. However, when the thickness of Si 0.8 Ge 0.2 film was increased to 80 nm, QDMs appeared both inside the windows and in the unpatterned areas, and the density of QDMs was reduced with the decrease in the window size. We attribute these results to the different strain relaxations in different size windows, which are caused by the edge effect of the epitaxial film in the window. Based on these experimental results we discuss the formation and the size stability of the QDMs and conclude that the formation of the SiGe QDM originates from an intrinsic cause of the strain relief mechanism. This work also shows that by means of the edge induced strain relaxation of the epitaxial film in the window, it is possible to reveal the influence of the strain on some physical properties of the SiGe film without changing its Ge atomic fraction.