  Core-shell germanium nanowire (GeNW) is formed with a single-crystalline Ge
core and concentric shells of nitride and silicon passivation layer by chemical
vapor deposition (CVD), an Al2O3 gate dielectric layer by atomic layer
deposition (ALD) and an Al metal surround-gate (SG) shell by isotropic
magnetron sputter deposition. Surround gate nanowire field effect transistors
(FETs) are then constructed using a novel self-aligned fabrication approach.
Individual SG GeNW FETs show improved switching over GeNW FETs with planar gate
stacks owing to improved electrostatics. FET devices comprised of multiple
quasi-aligned SG GeNWs in parallel are also constructed. Collectively, tens of
SG GeNWs afford on-currents exceeding 0.1mA at low source-drain bias voltages.
The self-aligned surround gate scheme can be generalized to various
semiconductor nanowire materials.
