Silicon nanowires: Catalytic growth and electrical characterization

Nominally undoped silicon nanowires (NW) were grown by catalytic chemical vapor deposition. The growth process was optimized to control the NWs diameters by using different Au catalyst thicknesses on amorphous SiO₂, Si ₃N₄, or crystalline-Si substrates. For SiO₂ substrates an Ar plasma treatment was used to homogenize the catalyst coalescence, and thus the NWs diameter. Furthermore, planar field effect transistors (FETs) were fabricated by implementing 13 to 30 nm thin nominally undoped Si-NWs as the active region. Various suicides were investigated as Schottky-barrier source and drain contacts for the active region. For CoSi, NiSi and PdSi contacts, the FETs transfer characteristics showed p-type behavior. A FET consisting of a single Si-NW with 20 nanometers diameter and 2.5 μm gate-length delivers as much as 0.15 μA on-current at 1 volt bias voltage and has an on/off current ratio of 10⁷. This is in contrast to recent reports of low conductance in undoped Si.