Demonstration of Schottky barrier NMOS transistors with erbium silicided source/drain and silicon nanowire channel

We have fabricated silicon nanowire N-MOSFETs using erbium disilicide ErSi_2-x in a Schottky source/drain back-gated architecture. Although the subthreshold swing (∼180 mV/dec) and drain-induced barrier lowering (∼500 mV/V) are high due thick BOX as gate oxide, the fabricated Schottky transistors show acceptable drive current ∼900 μA/m and high I_onI/_off ratio ∼10⁵. This is attributed to the improved carrier injection as a result of low Schottky barrier height (Phi_b) ErSi_2-x/n - Si(∼0.3 eV) and the nanometer-sized (∼8 nm) Schottky junction. The carrier transport is found to be dominated by the metal-semiconductor interface instead of the channel body speculated from the channel length independent behavior of the devices. Furthermore, the transistors exhibit ambipolar characteristics, which are modeled using thermionic/thermionic-field emission for positive and thermionic-field emission for negative gate biases.