  We evidence the influence of surface effects for InAs quantum dots embedded
into GaAs photonic nanowires used as efficient single photon sources. We
observe a continuous temporal drift of the emission energy that is an obstacle
to resonant quantum optics experiments at the single photon level. We attribute
the drift to the sticking of oxygen molecules onto the wire, which modifies the
surface charge and hence the electric field seen by the quantum dot. The
influence of temperature and excitation laser power on this phenomenon is
studied. Most importantly, we demonstrate a proper treatment of the nanowire
surface to suppress the drift.
