Realization and Scaling of ${\rm Ge}{\hbox{--}}{\rm Si}_{1{\hbox{-}}{\rm x}}{\rm Ge}_{\rm x}$ Core-Shell Nanowire $n$-FETs

We present the realization and scaling properties of germanium-silicon-germanium (Ge-Si
_1-x
Ge
_x
) core-shell nanowire (NW) n-type, Ω-gate field-effect transistors (FETs). The devices show superior performance to the counterparts without the Si
_1-x
Ge
_x
shell. With a channel length (L
_ch
) of 380 nm and a diameter of 40 nm, we demonstrate a subthreshold swing of 180 mV/dec, and an ON-current (ION) of 60 μA/μm, comparable with recent results in Ge n-type FinFETs fabricated by top-down techniques. By systematically studying the scaling properties, we identify the contribution of the channel and contact resistances to device characteristics. We conclude that I
_ON
is not limited by the contact resistance but rather by a relatively large channel resistance, presumably associated with a high-interface trap density (D
_it
).