Substitutional sites of Co2+ ions in CuGa1−xAlxSe2:Co2+ crystals

The substitutional sites of Co2+ ions in Co2+-doped CuG1−xAlxSe2 (including CuGaSe2 where x=0 and CuAlSe2 where x=1) semiconductors are studied by analyzing the composition x dependence of optical spectral parameters reported in the previous literature for these materials. From the studies, we suggest that Co2+ occupy I-group cation site rather than III-group cation site. The suggestion is discussed.