The reflectivity spectra of Zn XP 2 ( X=Si, Ge, and Sn) compounds

Full Potential Augmented Plane Wave plus local orbital method ( FAPW+ lo) calculations were performed for ZnSiP ₂, ZnGeP ₂, and ZnSnP ₂ in the chalcopyrite structure in order to investigate the optical properties and to show the origin of the different optical transitions and their correspondence in the band structure. It is found that the most important features of the band gap is pseudo-direct for ZnSiP ₂, indirect for ZnGeP ₂, and direct for ZnSnP ₂. Then the contribution of the different transitions peaks are analyzed from the imaginary part of the dielectric function and the reflectivity spectra.