Ge<sub>0.95</sub>Sn<sub>0.05</sub> Gate-All-Around p-Channel Metal-Oxide-Semiconductor Field-Effect Transistors with Sub-3 nm Nanowire Width.

Kang, Yuye; Xu, Shengqiang; Han, Kaizhen; Kong, Eugene Y-J; Song, Zhigang; Luo, Sheng; Kumar, Annie; Wang, Chengkuan et al. · Nano Lett · 2021

basic_science · Level V

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Abstract

We demonstrate Ge<sub>0.95</sub>Sn<sub>0.05</sub> p-channel gate-all-around field-effect transistors (p-GAAFETs) with sub-3 nm nanowire width (<i>W</i><sub>NW</sub>) on a GeSn-on-insulator (GeSnOI) substrate using a top-down fabrication process. Thanks to the excellent gate control by employing an aggressively scaled nanowire structure, Ge<sub>0.95</sub>Sn<sub>0.05</sub> p-GAAFETs exhibit a small subthreshold swing (SS) of 66 mV/decade, a decent on-current/off-current (<i>I</i><sub>ON</sub>/<i>I</i><sub>OFF</sub>) ratio of ∼1.2 × 10<sup>6</sup>, and a high-field effective hole mobility (<i>μ</i><sub>eff</sub>) of ∼115 cm<sup>2</sup>/(V s). In addition, we also investigate quantum confinement effects in extremely scaled GeSn nanowires, including threshold voltage (<i>V</i><sub>TH</sub>) shift and <i>I</i><sub>OFF</sub> reduction with continuous scaling of <i>W</i><sub>NW</sub> under 10 nm. The phenomena observed from experimental results are substantiated by the calculation of GeSn bandgap and TCAD simulation of electrical characteristics of devices with sub-10 nm <i>W</i><sub>NW</sub>. This study suggests Ge-based nanowire p-FETs with extremely scaled dimension hold promise to deliver good performance to enable further scaling for future technology nodes.