Epitaxial growth of peculiar GeSn and SiSn nanostructures using a Sn island array as a seed

Abstract

The regularities of the GeSn and SiSn nanostructure formation on Si and Ge(100) substrates on the vapor–liquid-crystal mechanism were studied. It was shown that either thread-like nanostructures or mushroom-shaped islands containing truncated icosahedrons in the upper Ge part can appear on a Ge(100) substrate. A Sn-rich island array with faceted silicon pedestals was formed during the Si growth over the Sn island array obtained on a Si(100) substrate. Two characteristic island shapes with lenticular and conical shapes were found by transmission electron microscopy (TEM). Lenticular islands consist of β-Sn and are buried in Si, while cone-shaped islands, in addition to β-Sn, contain a SiSn solid solution region in their lower part. The Sn content, estimated from interplanar spacing changes, is about 5%. The region between the islands also contains the SiSn solid solution layer. In addition, it has a nanostructured faceted morphology. The photoluminescence signal from structures with the SiSn island array with silicon pedestals was observed in the region from 1.25 to 3 μm with a maximum of about 2 μm. The nanostructured faceted surface formation was studied by self-organization. The appearance of GeSn cross-structures was revealed during the GeSn deposition on a nanostructured faceted surface. The near-infrared photoluminescence increase by a factor of 3.5 was demonstrated in the samples with cross-structures.