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

Abstract

High quality InN nanoparticles are grown using an atmospheric chemical vapour deposition technique via a self-seeded catalytic approach in the temperature range of 580–650 °C. In this temperature region, the nucleation barrier of InN is overcome by seeding low density In nanoparticles prior to introduction of reactive NH₃. Samples with increasing carrier densities are grown, with the help of increasing growth temperature, to understand the role of carrier density in the optical phonon structure. Near-resonance Raman spectra show completely different phonon pictures compared to those for the off-resonance spectra. A Raman forbidden mode of B₁(high), because of the possible breakdown of selection rules in the near-resonance conditions, is invoked for the first time. The intensity and frequency of this mode strongly depend on the carrier concentration in the sample. In off-resonance conditions, the A₁(LO) mode for the sample with higher carrier concentration is dominated by Fano interference rather than plasmon–phonon coupling. Variation of the intensity of the B₁(high) mode is correlated with a band filling effect, which is substantiated by the luminescence studies of the InN samples with different carrier concentrations.