Using photoluminescence and deep-level transient spectroscopy, the concentration changes of Cu-related centers in Si crystals saturated with Cu at 600 to 1000C were observed. Each sample was measured at the same location for both methods. The deep-level transient spectroscopy peak, assigned to have the same origin as the 1.014eV photoluminescence center (CuPL center), was clearly the strongest component among the deep-level transient spectroscopy peaks. No deep-level transient spectroscopy peak due to isolated substitutional Cu (Cus) was observed for any of the diffusion temperatures used. The photoluminescence and deep-level transient spectroscopy intensities of the CuPL center increased with increasing diffusion temperature of Cu from 600 to 700C, reached a maximum between 700 and 800C, then sharply decreased at higher temperatures than 800C. This behavior was reasonably explained by considering the out-diffusion and precipitation of Cu in addition to the solubility of Cu. The maximum deep-level transient spectroscopy concentration of the CuPL center (∼1014/cm3) observed in the present study far exceeded the estimated concentration of Cus formed through a vacancy-mediated reaction. From this finding, it was concluded that a model containing Cus was invalid for the CuPL center and that another model containing unique Cu atom at the center of the Si–Si bond was realistic.

Diffusion-Temperature-Dependent Formation of Cu Centers in Cu-Saturated Silicon Crystals Studied by Photoluminescence and Deep-Level Transient Spectroscopy. M.Nakamura, S.Murakami, N.J.Kawai, S.Saito, H.Arie: Japanese Journal of Applied Physics, 2008, 47, 4398-402