  Realizing single photon sources emitting in the telecom band on silicon
substrates is essential to reach complementary-metal-oxide-semiconductor (CMOS)
compatible devices that secure communications over long distances. In this
work, we propose the monolithic growth of needlelike tapered InAs/InP quantum
dot-nanowires (QD-NWs) on silicon substrates with a small taper angle and a
nanowire diameter tailored to support a single mode waveguide. Such a NW
geometry is obtained by a controlled balance over axial and radial growths
during the gold-catalyzed growth of the NWs by molecular beam epitaxy. This
allows us to investigate the impact of the taper angle on the emission
properties of a single InAs/InP QD-NW. At room temperature, a Gaussian
far-field emission profile in the telecom O-band with a 30{\deg} beam
divergence angle is demonstrated from a single InAs QD embedded in a 2{\deg}
tapered InP NW. Moreover, single photon emission is observed at cryogenic
temperature for an off-resonant excitation and the best result, $g^2(0) =
0.05$, is obtained for a 7{\deg} tapered NW. This all-encompassing study paves
the way for the monolithic growth on silicon of an efficient single photon
source in the telecom band based on InAs/InP QD-NWs.
