First-principles study of charge states effects of nitrogen vacancies on phonon properties in III-nitride semiconductors

Understanding the effects of defects on the phonon-related properties of III-nitride semiconductors is important for device applications. However, the effect of the charge-state difference on the phonon-related properties of defects has not been studied. This study calculated the phonon bands of AlN and GaN for pristine crystals and crystals with +1 or +3 nitrogen vacancies ( or ). Our results revealed distinct differences in the phonon bands, density of states (DOS), and infrared (IR) spectra between pristine and defective crystals, particularly between and . The exhibited a larger disturbance in the phonon bands than . The exhibited more peaks and larger peak intensities in the DOS than . The IR spectrum intensity of (TO) was larger than that of (TO) in the , which was different from the pristine and cases. In the IR spectrum of in GaN, a small peak appeared to represent a defect. These results imply that the effects of vacancies on the phonon-related properties depend not only on the concentration but also on the charge state. This study can serve as a guide for future in-depth research on the effect of defects on thermal properties.