Diffusion-Temperature-Dependent Formation of Cu Centers in Cu-Saturated Silicon Crystals Studied by Photoluminescence and Deep-Level Transient Spectroscopy

Using photoluminescence (PL) and deep-level transient spectroscopy (DLTS) we observed the concentration changes of Cu-related centers in silicon crystals saturated with Cu at various temperatures (600–1000 °C), in which each sample was measured at the same location for both methods. The DLTS peak assigned to have the same origin as the 1.014 eV PL center (CuPL center) was by far the strongest component among the DLTS peaks, and no DLTS peak due to isolated substitutional Cu (Cus) was observed for any of the diffusion temperatures used. The PL and DLTS intensities of the CuPL center increased with increasing diffusion temperature of Cu from 600 to 700 °C, reached a maximum between 700 and 800 °C, then sharply decreased at higher temperatures than 800 °C. This behavior was reasonably explained by considering the outdiffusion and precipitation of Cu in addition to the solubility of Cu. The maximum DLTS concentration of the CuPL center (~1014 cm-3) observed in the present study far exceeded the estimated concentration of Cus formed through a vacancy-mediated reaction. From this finding we 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.