Enhanced formation of luminescent nanocrystal Si embedded in $Si/SiO_2$ superlattice

Abstract

Ever since the report on the luminescence of porous Si by Canham , the study of luminescent nanocrystalline Si (nc-Si) has been an extremely active field of research. In this thesis, we have discussed the effect of the excimer laser annealing and the Ni , which have been used in producing low temperature poly Si, on the formation of luminescent nanocrystal Si (nc-Si) embedded in Si/$SiO_2$ superlattice. Ni co-doped and Ni undoped amorphous Si/$SiO_2$ superlattices consist of 20 periods of 2nm thin Si layers and 5 nm thin $SiO_2$ layers. They were deposited on Si using electron cyclotron resonance plasma enhanced chemical vapor deposition, Ni co-doping was done with concurrent sputtering Ni. A thermal anneal of Ni undoped supelattice film at 1100℃ resulted in a weak nc-Si luminescence. Excimer laser anneal of the as-deposited Ni undoped superlattice film did not result in any nc-Si luminescence even though the energy density was sufficient to melt the Si layers. Excimer laser anneal following the thermal anneal resulted in a three-fold increase of the nc-Si luminescence intensity but a redshift of the luminescence peak by only 30 meV. The temperature dependence of the nc-Si luminescence spectra shape, lifetime, and intensity indicate that the primary effect of excimer laser anneal is the removal of defects and amorphous regions in thermally crystallized Si layers. And a thermal anneal of Ni co-doped superlattice film resulted in a two fold increase of the nc-Si luminescence intensity but a redshift of the luminescence peak by 100 meV. The temperature dependence of the nc-Si luminescence spectra lifetime and intensity indicate that the Ni increase crystal growth rate.