Sub-wavelength semiconductor nanowires have been attracting strong interest recently for photonic applications because they possess various unique optical properties and offer great potential for miniaturizing devices. However, with these nanowires, it is not easy to realize tight light confinement or efficient coupling with photonic circuits. Here we show that a high Q nanocavity can be created by placing a single III/V semiconductor nanowire with the diameter less than 100 nm in a grooved waveguide in a Si photonic crystal, and employing nanoprobe manipulation. We have observed very fast spontaneous emission (91 ps) from nanowires accelerated by the strong Purcell enhancement in nanocavities, which proves that unprecedented strong light confinement can be achieved in nanowires. Furthermore, this unique system enables us to move the nanocavity anywhere along the waveguide. This configuration provides us tremendous flexibility in integrated photonics because we can add and displace various functionalities of III/V nanocavity devices in Si photonic circuits.

III-V semiconductors have been intensively studied with the goal of realizing metal-oxide-semiconductor field-effect transistors (MOSFETs) with high mobility, a high on-off ratio, and low power consumption as next-generation transistors designed to replace current Si technology. Of these semiconductors, a narrow band-gap semiconductor InAs has strong Rashba spin-orbit interaction, thus making it advantageous in terms of both high field-effect transistor (FET) performance and efficient spin control. Here we report a high-performance InAs nanowire MOSFET with a gate-all-around (GAA) structure, where we simultaneously control the spin precession using the Rashba interaction. Our FET has a high on-off ratio (104~106) and a high field-effect mobility (1200 cm2/Vs) and both values are comparable to those of previously reported nanowire FETs. Simultaneously, GAA geometry combined with high- κ dielectric enables the creation of a large and uniform coaxial electric field (>107 V/m), thereby achieving highly controllable Rashba coupling (1 × 10−11 eVm within a gate-voltage swing of 1 V), i.e. an operation voltage one order of magnitude smaller than those of back-gated nanowire MOSFETs. Our demonstration of high FET performance and spin controllability offers a new way of realizing low-power consumption nanoscale spin MOSFETs.

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GaP, GaAs, and InP nanowires were grown on graphitic layers by the vapor-liquid-solid method in a metalorganic vapor phase epitaxy chamber. On graphene/SiC(0001), Au particles as catalyst were formed at the steps by controlling the Au deposition rate and the annealing temperature in a low-energy electron microscopy system. GaP nanowires were grown on this substrate, and it was found that vertical nanowires were formed at the steps of the surface. We also performed GaP, GaAs, and InP nanowire growth on graphite substrates. Free-standing nanowires were obtained for all three materials, although they were vertically, diagonally, and laterally-oriented at the same time. The results suggested that the growth at the steps is the key to growing nanowires vertically on graphene surface.

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