Emission and Absorption Lines of Free and Bound Excitons in CuGaS2 Crystals

CuGaS₂ crystals grown from different starting materials by the iodine transport method showed different bound exciton luminescence lines, and total of 5 bound exciton (BE) lines were observed. Two of them were seen in absorption as well. From the absorption, concentrations of BE trapping centers were estimated to be of the order of 1016cm¯3. The sharp line at 2.4997 eV is supposed to be due to excitons bound to interstitials. The lines at 2.4909, 2.4934 and 2.4942 eV were found to have lifetimes of ~150 ps.