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Surface analysis of epitaxially grown GeSn alloys with Sn contents between 15% and 18%
Author(s) -
Kormoš L.,
Kratzer M.,
Kostecki K.,
Oehme M.,
Šikola T.,
Kasper E.,
Schulze J.,
Teichert C.
Publication year - 2017
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.6134
Subject(s) - tin , epitaxy , materials science , molecular beam epitaxy , germanium , metastability , surface energy , analytical chemistry (journal) , layer (electronics) , spectroscopy , phase (matter) , nanotechnology , chemistry , optoelectronics , metallurgy , composite material , silicon , chromatography , physics , organic chemistry , quantum mechanics
Abstract Metastable Germanium–tin (GeSn) layers with rather high Sn content between 15% and 18% grown on Si substrates by molecular beam epitaxy were analyzed for the morphological changes on a surface before and after reaching critical layer parameters (thickness, Sn content, and growth temperature) for surface roughening. Atomic‐force microscopy investigations were performed as a function of thickness and separately for varying Sn concentrations in the GeSn layer. Epitaxial growth of metastable, uniform GeSn (15% Sn content) layers is obtained up to a critical thickness which increases from about 80 to above 200 nm by reducing the nominal growth temperature from 160 to 140 °C. Phase separation of the complete layer into tin‐rich surface protrusions and a Ge‐rich matrix takes place beyond the critical thickness. This surface roughening via phase separation was not observed in earlier investigations with lower Sn concentrations (<6%). Tin depletion in the GeSn matrix was confirmed by using energy‐dispersive X‐ray spectroscopy measurements showing residual Sn concentration below 5%. Additionally, creation of droplets with high concentration of tin on the surfaces was confirmed by energy‐dispersive X‐ray spectroscopy. Copyright © 2016 John Wiley & Sons, Ltd.