Propagation losses in undoped and n-doped polycrystalline silicon wire waveguides

摘要: Polycrystalline silicon (polySi) wire waveguides with width ranging from 200 to 500 nm are fabricated by solid-phase crystallization (SPC) of deposited amorphous (a-Si) on SiO2 at a maximum temperature 1000°C. The propagation loss 1550 decreases 13.0 9.8 dB/cm the waveguide shrinking 300 while 200-nm-wide exhibit quite large (>70 dB/cm) mainly due relatively rough sidewall induced polySi dry etch. By modifying process sequence, i.e., first patterning a-Si layer into etch and then SPC, roughness is significantly improved but crystallinity degraded, leading 13.9 in larger losses wider waveguides. Phosphorus implantation causes an additional doping-induced optical increases slowly phosphorus concentration increasing up 1 × 1018 cm−3, whereas 5 cm−3 doped dominant free carrier absorption. For all undoped waveguides, further 1–2 reduction obtained standard forming gas (10%H2 + 90%N2) annealing owing hydrogen passivation Si dangling bonds present achieving lowest 7.9 300-nm-wide However, for slightly increased annealing.