  Recently, heavily doped semiconductors are emerging as an alternate for low
loss plasmonic materials. InN, belonging to the group III nitrides, possesses
the unique property of surface electron accumulation (SEA) which provides two
dimensional electron gas (2DEG) system. In this report, we demonstrated the
surface plasmon properties of InN nanoparticles originating from SEA using the
real space mapping of the surface plasmon fields for the first time. The SEA is
confirmed by Raman studies which are further corroborated by photoluminescence
and photoemission spectroscopic studies. The frequency of 2DEG corresponding to
SEA is found to be in the THz region. The periodic fringes are observed in the
near-field scanning optical microscopic images of InN nanostructures. The
observed fringes are attributed to the interference of propagated and back
reflected surface plasmon polaritons (SPPs). The observation of SPPs is solely
attributed to the 2DEG corresponding to the SEA of InN. In addition, resonance
kind of behavior with the enhancement of the near-field intensity is observed
in the near-field images of InN nanostructures. Observation of SPPs indicates
that InN with SEA can be a promising THz plasmonic material for the light
confinement.
