PHONON-SPECTRUM OF WURTZITE GAN AND ALN EXPERIMENT AND THEORY

We present the results of a detailed study of the first and second-ord er Raman scattering in wurtzite GaN and AIN at room and liquid helium temperatures. A complete group-theory analysis of phonon symmetry and optical selection rules permitted us to assign the observed features i n the second-order Raman spectra to combinations of phonons at the Gam ma, K, and M points of the Brillouin zone. The joint treatment of thes e results with lattice dynamical calculations based on phenomenologica l interatomic potential model allowed us to obtain the reliable data o n phonon dispersion curves in bulk GaN and AIN. (C) 1998 Elsevier Scie nce B.V. All rights reserved.