  Using Finite-Difference Time-Domain (FDTD) simulation, we show that
ultrahigh- Q nanocavities can be obtained through the manipulation of a single
semiconductor nanowire (NW) inside a slot in a line defect of a two-dimensional
(2D) photonic crystal. By controlling the design and its lattice parameters of
the photonic crystal, we have achieved a quality factor Q larger than 106 and a
mode volume Vc smaller than 0.11 {\mu}m3 (1.25 of a cubic wavelength in the NW)
for a cavity peak in the telecommunication band. This design is useful for
realizing a position-controlled cavity in a photonic crystal. Here we also
discuss the small dependence of the Qfactor, the Vc, and the cavity peak in
relation to the position of the NWinside the slot and the potential application
to the cavity quantum electrodynamics (QED) using the embedded-emitter NW.
