  Nanowires (NWs) with a unique one-dimensional structure can monolithically
integrate high-quality III-V semiconductors onto Si platform, which is highly
promising to build lasers for Si photonics. However, the lasing from
vertically-standing NWs on silicon is much more difficult to achieve compared
with NWs broken off from substrates, causing significant challenges in the
integration. Here, the challenge of achieving vertically-standing NW lasers is
systematically analyzed. The poor optical reflectivity at the NW/Si interface
results severe optical field leakage to the substrate, and the commonly used
SiO2 or Si2N3 dielectric mask at the interface can only improve it to ~10%,
which is the major obstacle for achieving low-threshold lasing. A NW super
lattice distributed Bragg reflector is therefore proposed, which is able to
greatly improve the reflectivity to >97%. This study provides a highly-feasible
method to greatly improve the performance of vertically-standing NW lasers,
which can boost the rapid development of Si photonics.
