ABSTRACT:

1D semiconductor nanomaterials such as nanowires (NWs) and nanosheets (NSs) have attracted a lot of attention in the last two decades because of their appealing electrical, optical and mechanical properties. In the wide range of such materials, the NWs and NSs based on group IV elements deserve special consideration. Besides the extensively studied silicon (Si) and germanium (Ge), their alloys with tin (Sn) – GeSn and SiGeSn – are very promising due to a number of unique properties. Sn concentrations in the range of 3-15% allow effective bandgap engineering as well as achieving high charge carrier mobility and even a direct-bandgap group IV semiconductor. This makes the SiGeSn alloy systems ideal for post-Si-based nanoelectronic and optoelectronic applications since they combine the flexibility and mobility gain of III/V compound semiconductors and heterostructures with the well-developed Si processing technology.

In this talk, we will first discuss the top-down fabrication of Si, Ge and alloy NWs with varying content of the different elements (Si_1-x-yGe_ySn_x). Furthermore, we will consider their challenging structural and electrical characterisation, paying special attention to the transmission electron microscopy (TEM) and the Hall Effect measurements using a novel six-contact Hall bar configuration with symmetric contact bars located opposite to each other. This configuration allows reliable evaluation of the electrical properties of even very small nanowires with widths down to 20-30 nm as well as quantification of such parameters as carrier concentration (n), Hall mobility (µ_H), and resistivity (ρ).

Finally, some advanced nanoelectronic devices based on the fabricated NWs will be reviewed, in particular junctionless nanowire transistors (JNTs) and reconfigurable field effect transistors (RFETs). Different configurations of such devices will be discussed together with their structural and electrical characterisation. A special focus will be put on Si JNTs for sensing applications as well as on Si, Ge, SiGe, GeSn and SiGeSn JNTs and RFETs for digital logic.

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.