Formation of the photoluminescence Cu center on in-diffusion and out-diffusion of Cu in dilute Cu-contaminated silicon crystals

Abstract

Changes of photoluminescence (PL) intensity of the 1.014 eV Cu center (CuPL) with in- and out-diffusion of Cu in dilute Cu-contaminated silicon crystals (∼1013 atom/cm3) were observed. The intensity of CuPL increased with in-diffusion temperature of Cu to 700 °C and then decreased with increasing temperature above 800 °C for a short in-diffusion time. The formation barrier for CuPL (0.65 eV) obtained from the in-diffusion process of Cu below 600 °C was much smaller than the known effective formation enthalpy of an interstitial solution of Cu in silicon from Cu metal plated on silicon (1.5 eV), i.e., CuPL was formed more easily for a dilute Cu-contaminated sample than for a thickly Cu-plated sample. The decrease of the PL intensity of CuPL above 800 °C is attributed to the formation of another, more stable species than CuPL. A part of the in-diffused Cu out-diffused at room temperature after removing the surface oxide of the crystal for p-type crystals. Little change of CuPL intensity occurred on out-diffusion of Cu, indicating that CuPL and the out-diffusing species differed from each other. The changes of CuPL intensity on in- and out-diffusion processes of Cu were reasonably explained by assuming participation of several stable Cu species (at least three) in the silicon crystal.