A PL study of CIGS thin films implanted with He and D ions

Cu(InGa)Se-2 thin films deposited on Mo coated soda-lime glass substrates b y co-evaporation, were implanted with He+ and D+ (energies between 2.5 and 40 keV, doses from 10(14) to 3 x 10(15) cm(-2)) at room temperature. Implan ted and non-implanted areas of the films were characterised using low tempe rature photoluminescence (PL). A single broad band (Al) at 1.1 eV dominated in the PL spectra from the nonimplanted material. Also a long, low energy and low intensity tail with a well-defined band (AZ) at 0.78 eV was detecte d, implantation of either He or D reduced the band Al intensity. Three high intensity low energy peaks IH1, IH2, and IH3 were observed in the PL spect ra in both cases. One of the peaks (IH3) was detected at 0.78 eV. An increa se in either dose or energy of implantation was found to increase the inten sity of IH2 and IH3 normalised to that of Al. Similarities between the low energy bands observed after either He or D implantation suggests that all t he three bauds have intrinsic origins. It is speculated that the implanted ions accumulate in small bubbles or diffuse to the surface and grain bounda ries. The characteristics of bands A2 and IH3 suggest that the defects resp onsible fur the emission were present in the films before implantation. Lat tice recovery processes leading to an overall reduction in the primary impl ant-related defect population could produce additional defects, which are a ssociated with the low-energy PL peaks. (C) 2000 Elsevier Science S.A. All rights reserved.