LATTICE-DYNAMICS OF ZINCBLENDE GAN AND ALN .1. BULK PHONONS

The lattice dynamics of zinc-blende GaN and AlN were studied theoretic ally using a two-parameter Keating potential together with the long-ra nge Coulomb interactions. Phonon frequencies transformed from those of the wurtzite counterparts were used to determine the two Keating para meters and the effective charge. We present for the first time the pho non dispersion curves for zinc-blende GaN and AlN. An interesting feat ure was found for the phonons propagating along the [110] direction, w hich does not exist in other III-V semiconductors.