Surface analysis of epitaxially grown GeSn alloys with Sn contents between 15% and 18%. (7th September 2016)

• Record Type: Journal Article
• Authors: Kormoš, L.; Kratzer, M.; Kostecki, K.; Oehme, M.; Šikola, T.; Kasper, E.; Schulze, J.; Teichert, C.
• Is Part Of: Surface and interface analysis. Volume 49:Number 4(2017)
• Page Start: 297
• Page End: 302
• Publication Date: 2016-09-07
• Subjects: GeSn -- molecular beam epitaxy -- roughening -- atomic force microscopy (AFM) -- energy‐dispersive X‐ray spectroscopy (EDX) -- alloys; Surfaces (Physics) -- Periodicals; Surface chemistry -- Periodicals; Thin films -- Periodicals; 541.33
• DOI: 10.1002/sia.6134
• Languages: English
• ISSNs: 0142-2421

Abstract

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.