  An important consideration in miniaturizing transistors is maximizing the
coupling between the gate and the semiconductor channel. A nanowire with a
coaxial metal gate provides optimal gate-channel coupling, but has only been
realized for vertically oriented nanowire transistors. We report a method for
producing laterally oriented wrap-gated nanowire field-effect transistors that
provides exquisite control over the gate length via a single wet etch step,
eliminating the need for additional lithography beyond that required to define
the source/drain contacts and gate lead. It allows the contacts and nanowire
segments extending beyond the wrap-gate to be controlled independently by
biasing the doped substrate, significantly improving the sub-threshold
electrical characteristics. Our devices provide stronger, more symmetric gating
of the nanowire, operate at temperatures between 300 to 4 Kelvin, and offer new
opportunities in applications ranging from studies of one-dimensional quantum
transport through to chemical and biological sensing.
