PHONON DENSITY-OF-STATES OF BULK GALLIUM NITRIDE

We report the measured phonon density of states of a bulk GaN powder b y time-of-Right neutron spectroscopy. The observed one-phonon excitati on spectrum consists of two broad bands centered at about 23 and 39 me V corresponding to the acoustic and the first group of optical phonons ; two sharp bands of upper optic modes at about 75 and 86 meV; and a g ap of 45-65 meV. The phonon dispersion curves, lattice specific heat, and Debye temperature are calculated from fitting the data with a rigi d-ion model. (C) 1998 American Institute of Physics.