Excitation dependent Raman studies of self-seeded grown InN nanoparticles with different carrier concentration

High quality InN nanoparticles are grown using atmospheric chemical vapour deposition technique via a self-seeded catalytic approach in the temperature range of 580 to 650 oC. In this temperature region, nucleation barrier of InN is overcome by seeding the low density In nano-particles prior to the introduction of reactive ammonia. Samples having increasing carrier density are grown with the help of increasing growth temperature to understand its role in optical phonon structure. Near resonance Raman spectra show complete different phonon pictures as compared to those for the off-resonance spectra. A Raman forbidden mode of B1(high), because of the possible breakdown of selection rule in the near-resonance condition, is invoked for the first time. Intensity and frequency of this mode strongly depend on the carrier concentration in the sample. In off-resonance conditions, A1(LO) mode for the sample with high carrier concentration is dominated by Fano interference rather than plasmon-phonon coupling. Variation of intensity of the B1(high) mode is correlated with band filling effect, which is substantiated by the luminescence studies of the InN samples with different carrier concentration.