Lattice dynamics in GaN and AlN probed with first‐ and second‐order Raman spectroscopy

We present a selection of our contributions to basic research on the lattice dynamical properties of group‐III nitrides and their alloys. We used first‐order Raman scattering to determine the zone‐center phonons and their dependence on structural attributes such as stress, chemical composition, impurities, and doping. Results on the angular dispersion of the polar modes, strain distribution, coupled LO‐phonon plasmon modes, multi‐mode behavior in Al x Ga 1− x N, and the quantitative determination of the phase purity of cubic and hexagonal GaN are shown. Second‐order Raman‐scattering experiments on GaN and AlN provide information on the vibrational states throughout the entire Brillouin zone. Based on a comparison of experimental data and calculated phonon‐dispersion curves we assigned the observed structures to particular phonon branches and points in the Brillouin zone. We also discuss the behavior of the optical modes under large hydrostatic pressure. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)