EFFECTS OF 6 MeV ELECTRON IRRADIATION ON PHOTOLUMINESCENCE OF HIGH-QUALITY CuInSe_2 SINGLE CRYSTALS

摘要

High-quality single crystals of CuInSe_2 with near-stoichiometric elemental compositions, grown by the Bridgman method, were irradiated by 6 MeV electrons with doses from 5·10~(15) to 10~(18) cm~(-2). The crystals were studied before and after irradiation using photoluminescence (PL) at a temperature of 4.2 K. The PL spectra, measured before the irradiation, reveal a number of sharp and well resolved lines associated with free-and bound-excitons. The lower energy region of the spectra also reveals broader peaks related to band-impurity, donor-acceptor pair recombination and their phonon replicas. The irradiation resulted in a reduction of the intensity of the free- and bound-excitons observed in the non-implanted material. Such a reduction is observed for quite low doses of 5·10~(15) cm~(-2). Irradiation also induces new sharp PL lines W1 at 1.03, W_2 at 1.01 eV and W_3 eV at 0.99 eV below the free-exciton emission. Two deeper broad bands, associated earlier with the acceptor-type defects, interstitial selenium (Se_i) and copper on indium site (Cu_(In)), have become more intense suggesting an increase in the concentration of these defects due to irradiation.