title: Ge/Si nanowire heterostructures as high-performance field-effect transistors.
abstract: Semiconducting carbon nanotubes and nanowires are potential alternatives to planar metal-oxide-semiconductor field-effect transistors (MOSFETs) owing, for example, to their unique electronic structure and reduced carrier scattering caused by one-dimensional quantum confinement effects. Studies have demonstrated long carrier mean free paths at room temperature in both carbon nanotubes and Ge/Si core/shell nanowires. In the case of carbon nanotube FETs, devices have been fabricated that work close to the ballistic limit. Applications of high-performance carbon nanotube FETs have been hindered, however, by difficulties in producing uniform semiconducting nanotubes, a factor not limiting nanowires, which have been prepared with reproducible electronic properties in high yield as required for large-scale integrated systems. Yet whether nanowire field-effect transistors (NWFETs) can indeed outperform their planar counterparts is still unclear. Here we report studies on Ge/Si core/shell nanowire heterostructures configured as FETs using high-kappa dielectrics in a top-gate geometry. The clean one-dimensional hole-gas in the Ge/Si nanowire heterostructures and enhanced gate coupling with high-kappa dielectrics give high-performance FETs values of the scaled transconductance (3.3 mS microm(-1)) and on-current (2.1 mA microm(-1)) that are three to four times greater than state-of-the-art MOSFETs and are the highest obtained on NWFETs. Furthermore, comparison of the intrinsic switching delay, tau = CV/I, which represents a key metric for device applications, shows that the performance of Ge/Si NWFETs is comparable to similar length carbon nanotube FETs and substantially exceeds the length-dependent scaling of planar silicon MOSFETs.
authors.affiliation: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Xiang
authors.forename: Wei
authors.initials: W
authors.lastname: Lu
authors.forename: Yongjie
authors.initials: Y
authors.lastname: Hu
authors.forename: Yue
authors.initials: Y
authors.lastname: Wu
authors.forename: Hao
authors.initials: H
authors.lastname: Yan
authors.forename: Charles M
authors.initials: CM
authors.lastname: Lieber
mesh_terms: D005857:Germanium / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D037742:Nanotubes, Carbon / Q000737:chemistry; D012825:Silicon / Q000737:chemistry*; D014173:Transistors, Electronic
chemical_list: D037742:Nanotubes, Carbon; D005857:Germanium; D012825:Silicon