Observation of local vibrational modes in N-doped 6H-SiC

Doping plays a vital role in tuning the carrier concentration and also influences various electronic properties in semiconductors. In addition to tuning the electronic properties of semiconductors, impurities also affect vibrational properties. We report the local vibrational modes (LVMs) in N-doped n -type 6H-SiC. New phonon modes are observed in the low-temperature range. Unlike lattice phonons, LVMs are localized in both the real space and frequency domains and give rise to a distinct signature in the Raman spectra. In the present study, LVMs in N-doped 6H-SiC are identified as N atom vibrations with the help of lattice dynamical calculations of the phonon density of states using generalized gradient approximation. Moreover, the stability of the SiC is investigated for a wide temperature range signifying its application in micro-electro-mechanical systems technology. Therefore, the present study provides insight for understanding both lattice phonons and the impurity-induced vibrational modes using Raman spectroscopic analysis in corroboration with the calculation of phonon density of states.