Physical characteristics of III-V nitride nanowires grown by the self-catalytic chemical vapor deposition method have been studied. The nanowire shape (uniform or tapered) and nanowire branching are found to depend on a number of parameters that influence the nanowire growth. Among them, the Gibbs-Thompson effect and the diffusivity of adatoms through liquid droplet dictate the length-to-diameter relationship of nanowires. The Raman scattering spectrum shows that the nanowires exist primarily in the hexagonal phase. Local modes, electronic transitions of dopant atoms, and impurity atoms contribute to unexpected peaks in this spectrum. (c) 2007 American Vacuum Society.