First principles calculations of phonons and Raman and infrared spectra in ZnGeGa₂N₄ .

ZnGeN₂ is a semiconductor compound closely related to GaN. They have similar band gaps and are closely lattice matched but have a large band-offset, which enables new capabilities in heterostructure and alloy band structure engineering. Recently, a well-defined crystal structure with space group Pmn2₁ was proposed for the 50% compound ZnGeGa₂N₄ which satisfies the local octet rule around each N [PHYSICAL REVIEW MATERIALS2, 114602 (2018)]. Here, a first-principles study of the phonons in this material is presented. The calculations are performed using the density functional perturbation theory within the ABINIT software. The phonon frequencies at the Brillouin zone center and their symmetry analysis, as well as various associated parameters, will be presented: Born effective charge tensors, oscillator strength tensors,
dielectric constants. The infrared and Raman spectra have been calculated for various scattering configurations. The phonon density of states and phonon dispersion curves will also be reported.