Hot-wire polysilicon waveguides with low deposition temperature.

We fabricated and measured the optical loss of polysilicon waveguides deposited using hot-wire chemical vapor deposition at a temperature of 240°C. A polysilicon film 220 nm thick was deposited on top of a 2000 nm thick plasma-enhanced chemical vapor deposition silicon dioxide layer. The crystalline volume fraction of the polysilicon film was measured by Raman spectroscopy to be 91%. The optical propagation losses of 400, 500, and 600 nm waveguides were measured to be 16.9, 15.9, and 13.5 dB/cm, respectively, for transverse electric mode at the wavelength of 1550 nm. Scattering loss is expected to be the major contributor to the propagation loss.