Chapter 2: High Performance, Low Power Nanowire Transistor Devices

Nanowire field-effect transistors (NW-FETs) have been studied and developed by many research groups around the world as a promising candidate to sustain the relentless cadence of device scaling. Several key factors contributed to the boom of nanowire research. First, semiconductor nanowires can be prepared with reproducible electronic properties in high-yield, as required for large-scale integrated systems. Second, compared with “top-down” nanofabricated device structures, the “bottom-up” synthesized nanowire materials offer well-controlled size in at least one critical device dimension that is at or beyond the limits of lithography. In addition, the crystalline structure and smooth surfaces reduce scattering and result in higher carrier mobility compared with nanofabricated samples with similar size. Third, since the body thickness (diameter) of nanowires can be controlled down to well below 10 nm, the electrical integrity of nanowire-based electronics can be maintained even as the gate length is aggressively scaled, a feat that has become increasingly difficult to achieve in conventional MOSFETs. Lastly, the unique dimensions and composition control allows new transistor mechanisms that can transcend the traditional thermodynamic limit to a transistor off-state current, using quantum mechanical tunneling, impact ionization as well as nanoelectromechanical motions, which will be required to meet the power challenge facing the ever increasing computing demands of future decades.