Sn-guided self-grown Ge stripes banded by GeSn Nanowires: Formation mechanism and electric-field-induced switching from p- to n-type conduction

• Published in: Applied surface science 2022-12, Vol.604, p.154443, Article 154443
• Main Authors: Kuchuk, A.V., Lytvyn, P.M., Mazur, Yu.I., Stanchu, H., Kondratenko, S.V., de Oliveira, F.M., Malyuta, S.V., Teodoro, M.D., Benamara, M., Yu, S.-Q., Salamo, G.J.
• Format: Article
• Language: English
• Subjects: Carrier distribution; Droplet; GeSn; Nanostructures; Tin segregation
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2022.154443

[Display omitted] •Ge(Sn) nanostructures are catalyzed by Sn surface droplets during the growth of Ge1-xSnx epilayers.•The mechanism of crystallographically directed self-growth Ge stripes is discussed.•The discrete jumping of the Sn droplet back edge resulting in the Ge stripes periodically banded by Ge1-xSnx nanowires.•An electric field induced reversible p- to n-type conduction switching effect in Ge(Sn) nanostructures is discovered. The formation of GeSn nanostructures catalyzed by Sn surface droplets during the growth of Ge1-xSnx/Ge/Si(001) heterostructures provide a promising strategy for the growth of high-quality Sn-containing group-IV alloys. The droplet formation is favored by Sn segregation at dislocation cores and diffusion of Sn towards the sample surface. Subsequent Sn droplet motion along 〈110〉 crystallographic directions result in self-assembled Ge stripes along the droplet’s path. A novel phenomenon is observed, for which Sn-rich GeSn nanowires (NWs) were periodically formed on top of Ge(Sn) stripes. While the front edge of the liquid Sn droplet is continuously moving and dissolving the Ge1-xSnx epilayer, the phenomenon of NW periodicity is explained by discrete jumping of the back edge of the droplet resulting in redeposition of material forming the NWs. It is also demonstrated that sn-induced phase separation of metastable Ge1-xSnx epilayers leads to carrier redistribution and an electric-field-induced conductivity type conversion from p- to n-type in the Ge(Sn) stripes. These results advance our understanding of the Sn segregation and phase separation mechanism for Ge1-xSnx epilayers at relatively low temperature (≥230 °C). This study could pave the way for understanding the droplet epitaxy synthesis of Sn-rich GeSn nanostructures generating emergent functionalities of GeSn-based nanodevices.