Defect-related photoluminescence of epitaxial CuInS2

Using molecular beam epitaxy (MBE), CuInS2 (CIS) films have been grown on 4-in Si(111) substrates. For a detailed investigation by means of photoluminescence (PL) spectroscopy, samples were either taken as grown or subjected to postgrowth treatments, including KCN etching and hydrogen implantation. Altogether, six defect-related transitions at 1.48 (#1), 1.436 (#2), 1.395 (#3), 1.345 (#4), 1.195 (#5) and 1.03 eV (#6) were observed and analysed by means of power-dependent measurements. Thus, one free-to-bound (#1) and five donor–acceptor transitions (#2–#6) were identified. The energetically highest of these observed transitions were combined in a model for intrinsic defect levels which includes two acceptor and one donor states.