Polarization of defect related optical transitions in chalcopyrites

We investigate the symmetry of shallow acceptors in Cu chalcopyrites by polarization dependent photoluminescence measurements and density functional calculations. We determine the influence of the band symmetry versus the site symmetry. The polarization of the emitted or absorbed light is parallel to the $c$-axis in the case of $CuGaSe2$ and perpendicular to the $c$-axis in the case of $CuInSe2$⁠. The symmetry of the defects depends in each case on the symmetry of the topmost band. Neither does the site symmetry affect the defect symmetry nor do the defects change the symmetry of the band.