Selective growth of fully relaxed GeSn nano-islands by nanoheteroepitaxy on patterned Si(001)

• Published in: Applied physics letters 2016-11, Vol.109 (20)
• Main Authors: Schlykow, V., Klesse, W. M., Niu, G., Taoka, N., Yamamoto, Y., Skibitzki, O., Barget, M. R., Zaumseil, P., von Känel, H., Schubert, M. A., Capellini, G., Schroeder, T.
• Format: Article
• Language: English
• Subjects: Applied physics; Crystal defects; Crystal structure; Crystallinity; Epitaxial growth; Interdiffusion; Islands; Molecular beam epitaxy; Photoluminescence; Red shift; Silicon dioxide; Silicon substrates; Stacking faults; Tin; Transmission electron microscopy; X-ray diffraction
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4967500

In this letter, we explore in detail the potential of nanoheteroepitaxy to controllably fabricate high quality GeSn nano-structures and to further improve the crystallinity of GeSn alloys directly grown on Si(001). The GeSn was grown by molecular beam epitaxy at relatively high temperatures up to 750 °C on pre-patterned Si nano-pillars embedded in a SiO2 matrix. The best compromise between selective GeSn growth and homogenous Sn incorporation of 1.4% was achieved at a growth temperature of 600 °C. X-ray diffraction measurements confirmed that our growth approach results in both fully relaxed GeSn nano-islands and negligible Si interdiffusion into the core of the nanostructures. Detailed transmission electron microscopy characterizations show that only the small GeSn/Si interface area reveals defects, such as stacking faults. Importantly, the main part of the GeSn islands is defect-free and of high crystalline quality. The latter was further demonstrated by photoluminescence measurements where a clear redshift of the direct ΓC-ΓV transition was observed with increasing Sn content.