5. Diamond-Shaped Ge Nanowire FETs
Category: Alternatives to Silicon
Paper 15.1 – Diamond-shaped Ge and Ge0.9Si0.1 Gate-All-Around Nanowire FETs with Four {111} Facets by Dry Etch Technology; Yao-Jen Lee et al, National Nano Device Laboratories/National Chiao Tung University/National Chi Nan University
Silicon and germanium have crystalline atomic structures which, like other crystals, have different facets. The materials’ electrical properties can vary according to which facet is used to build devices, and some facets are more favorable than others. A team led by Taiwan’s National Nano Device Laboratories will describe how they built gate-all-around (GAA) nanowire MOSFETs with diamond-shaped Ge and GeSi nanowire channels. The purpose of the work was to find a way to more effectively use germanium (Ge) as the channel material in multi-gate device configurations, because high-mobility Ge is seen as potentially necessary for scaling beyond the 10-nm technology node. Using common dry etching and blanket epitaxy techniques, the researchers sculpted Ge and GeSi nanowires into diamond cross-sectional shapes, with four favorable facets (the so-called {111} orientation) exposed. They used these nanowires as suspended channels in a GAA MOSFET configuration. Both nFET and pFET transistors with excellent performance were demonstrated, including pFETs with an Ion/Ioff ratio exceeding 108, the highest ever reported for Ge-based pFETs.
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