[21p-B201-1~16] 15.4 III-V-group nitride crystals

▲ [21p-B201-6] Theoretical Study of Effects of Nitrogen Vacancy on Phonon Dispersions of III-Nitride Semiconductors

〇Ying Dou^1,2, Koji Shimizu^1,2, Hiroshi Fujioka^1,3, Satoshi Watanabe^1,2 (1.Tokyo Univ., 2.School of Eng., 3.IIS)

Keywords:DFT, phonon, III-nitrides

We examined phonon bands for III-nitrides including defects, especially nitrogen vacancy in +1 and +3 charge state, from first principles. By unfolding the phonon bands of the models with N vacancy to the Brillouin zone of the pristine model, we have found that (1) splitting due to the introduction of defect with periodic boundary conditions appears in several bands and (2) features of acoustic phonon bands of the pristine crystal are relatively well kept while those of optical ones are more disturbed. Most importantly, distinct difference of phonon bands is seen between the cased of +1 and +3. That is, the change of the phonon bands, such as the phonon softening in optical modes, is more obvious in systems with +3 than those with +1. These results imply that the effects of vacancy on phonon-related properties depends not only on its density, but also on its charge state.