The phonon densities of states of wurtzite AlN and ZrN

Phonons are thought to play a crucial role in the high thermal conductivity of wide-bandgap semiconductors AlN and ZrN. Using time-of-flight neutron spectroscopy, we have measured the phonon spectra of AIN and ZrN up to 300 MeV (2400 cm{sup {minus}1}). The one-phonon density of states (DOS) of AIN exhibits relatively sharp bands at about 033, 63, 83 and 91 MeV. In addition, distinct multiple-phonon excitations were observed at {approximately}173 and 255 MeV. The phonon DOS of ZrN displays similar features with the corresponding phonon energies shifted toward lower energies. The measured DOS of AlN is compared with results of molecular-dynamics simulations