Hot-wire polysilicon waveguides with low deposition temperature.

Area of Science:

• Materials Science
• Optical Engineering
• Nanotechnology

Background:

• Polysilicon is a promising material for integrated photonics due to its compatibility with silicon fabrication processes.
• Optical waveguides are essential components in photonic integrated circuits for guiding light.
• Reducing optical loss in waveguides is crucial for improving device performance and enabling complex photonic systems.

Purpose of the Study:

• To fabricate and characterize polysilicon waveguides using hot-wire chemical vapor deposition (HWCVD).
• To measure the optical propagation losses of these waveguides at a wavelength of 1550 nm.
• To investigate the potential of HWCVD polysilicon for low-loss photonic applications.

Main Methods:

• Polysilicon films were deposited using HWCVD at 240°C on a silicon dioxide layer.
• Waveguides with widths of 400, 500, and 600 nm were fabricated.
• Optical propagation losses were measured using the transverse electric (TE) mode at 1550 nm.
• Raman spectroscopy was employed to determine the crystalline volume fraction of the polysilicon film.

Main Results:

• A crystalline volume fraction of 91% was achieved in the polysilicon film.
• Optical propagation losses were measured to be 16.9 dB/cm (400 nm), 15.9 dB/cm (500 nm), and 13.5 dB/cm (600 nm).
• Lower loss was observed for wider waveguides, suggesting scattering as a dominant loss mechanism.

Conclusions:

• HWCVD is a viable technique for depositing high-quality polysilicon for optical waveguides.
• The fabricated polysilicon waveguides exhibit competitive optical loss values.
• Further optimization, particularly addressing scattering losses, could lead to even lower loss polysilicon waveguides for integrated photonics.