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Group IV nanowires: fabrication, characterisation and applications

Khan, M. B.; Echresh, A.; Ghosh, S.; Arora, H.; Chava, P.; Jazavandi Ghamsari, S.; Khan, M. M.; Steuer, O.; Prucnal, S.; Hübner, R.; Rebohle, L.; Zhou, S.; Helm, M.; Erbe, A.; Georgiev, Y.

Semiconductor nanowires (NWs) attract significant attention due to their superb electrical and
mechanical properties and large surface area to volume ratio. They are promising building
blocks of devices for a number of possible applications such as nanoelectronics, nanophotonics,
photovoltaics, sensorics, etc. Among the large variety of semiconductor NWs, the ones based
on group IV elements – mainly silicon (Si), germanium (Ge) and their alloys with tin (Sn) (Si1-
x-yGeySnx) – stand out because of their appealing properties and superior compatibility with the
well-established silicon technology. This is an important prerequisite for their relatively easy
integration into the existing semiconductor fabrication platforms.

In the talk, the NWs that we work with will first be presented. These include top-down
fabricated Si and Ge NWs as well as nanowires of binary and ternary Si1-x-yGeySnx alloys with
varying content of the different elements.

Particular attention will be paid to structural and electrical characterisation of the nanowires
and especially to Hall Effect measurements using a novel six-contact Hall bar configuration
with symmetric contact bars located opposite to each other. Such a configuration with narrow
bars increases the precision of Hall contacts fabrication and enhances the accuracy of the Hall
Effect measurement by avoiding shorting out the Hall voltage. This allows to reliably evaluate
the electrical properties of even very small nanowires, down to 20-30 nm, and quantify their
carrier concentration (n), Hall mobility (μH), and resistivity (ρ).

The innovative nanoelectronic devices that we are targeting will also be discussed, namely
junctionless nanowire transistors (JNTs) and reconfigurable field effect transistors (RFETs).
We are in particular interested in Si JNTs for sensing application as well as in Ge, SiGe, GeSn
and SiGeSn JNTs for digital logic. In the case of RFETs, we are currently working on Si, SiGe
and GeSn RFETs and planning to work also on SiGeSn RFETs. Different configurations of
such devices will be discussed together with their structural and electrical characterisation.

Acknowledgments: This work was partially supported by the German Bundesministerium für
Bildung und Forschung (BMBF) under the project "ForMikro": Group IV heterostructures for
high performance nanoelectronic devices (SiGeSn NanoFETs), Project-ID: 16ES1075, and by
the European Union’s Horizon 2020 Research and Innovation programme under the project
RADICAL, Grant Agreement No. 899282. We gratefully acknowledge the HZDR Ion Beam
Centre and nanofabrication facility NanoFaRo.

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Publ.-Id: 36378