Abstract
It is shown that a study of the dependence of impurity-related resonant first-order Raman scattering on the frequency of excitation light makes it possible to observe the dispersion of polar optical and acoustic branches of vibrational spectrum in hexagonal InN within a wide range of wave vectors. It is established that the wave vectors of excited phonons are uniquely related to the energy of excitation photon. Frequencies of longitudinal optical phonons E 1 (LO) and A 1 (LO) in hexagonal InN were measured in the range of excitation-photon energies from 2. 81 to 1. 17 eV and the frequencies of longitudinal acoustic phonons were measured in the range 2. 81-1. 83 eV of excitation-photon energies. The obtained dependences made it possible to extrapolate the dispersion of phonons A 1 (LO) and E 1 (LO) to as far as the point Γ in the Brillouin zone and estimate the center-band energies of these phonons (these energies have not been uniquely determined so far). © 2010 Pleiades Publishing, Ltd.