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Optical properties and lattice dynamics of Cu 2 ZnGeSe 4 quaternary semiconductor: A density‐functional study

Density‐functional calculations of the electronic band structure, optical properties, and lattice dynamics of kesterite Cu 2 ZnGeSe 4 semiconductor (space group I4‾ ) are reported. Theoretical optical properties of the material are shown to agree quantitatively with available spectroscopic ellipsometry experimental data that allow detailed interpretation of the main spectral features around the fundamental absorption edge. A good agreement between theoretical and experimental vibrational mode frequencies is also established and the assignment of observed phonon modes to specific lattice eigenmodes is performed.