Observation of phonon sideband emission in intrinsic InN nanowires: a photoluminescence and micro-Raman scattering study

In this work, photoluminescence and micro-Raman scattering experiments were performed on undoped InN nanowires. It was found that, besides the main photoluminescence peak, a clear phonon sideband emission peak, with an extremely narrow linewidth similar to 9 meV, was measured. The phonon spectrum revealed by micro-Raman scattering indicates only uncoupled LO phonons are involved in such phonon sideband emission. The clearly resolved phonon sideband emission peak with a narrow linewidth, together with the uncoupled LO phonon modes, suggests the superior quality of the presented InN nanowires, i.e., extremely low residual electron density and the absence of surface electron accumulation, which is consistent with the physical properties of intrinsic InN nanowires as in the previous studies. The detailed phonon sideband properties are also discussed in the text.