Effects of carbon codoping on lattice locations of erbium in silicon

Abstract

The effects of carbon codoping on the lattice location of Er atoms in silicon have been investigated using ion beam channeling. A float-zone (FZ) Si (100) wafer was first amorphized to a depth of ∼0.3 μm by Si ion implantation at 77 K. The amorphous Si layer was then implanted with carbon ions, and recrystallized via solid phase epitaxial growth. Finally, Er ions were implanted into C-doped and C-free Si samples at 300 °C. Angular scans along three major crystalline directions, that is, 〈100〉, 〈110〉, and 〈111〉, were performed for Er-implanted Si with and without C codoping. In FZ-Si, in which the carbon concentration is very low (<1016 cm−3), a large fraction (∼50%) of implanted Er atoms are found to occupy the near-tetrahedral (T) interstitial site, while few Er atoms are on the hexagonal (H) interstitial site. It is evident that the incorporation of C into Si tends to decrease the fraction of T-site Er atoms and relocate them to the H site. We have also determined the effective number (∼1.5) of carbon atoms required for depopulating an Er atom from the T site to H site. Implications on the configuration of Er luminescence centers are discussed.