Ultra-low-temperature a-Si:H sputtering for high-quality photonic integration

Area of Science:

• Materials Science
• Photonics
• Semiconductor Device Fabrication

Background:

• Integrated silicon photonics requires materials with high refractive index and low optical loss.
• Traditional fabrication methods for amorphous silicon photonics often involve high temperatures, limiting integration options.

Purpose of the Study:

• To demonstrate the fabrication of high-quality hydrogenated amorphous silicon (a-Si:H) photonic devices using a low-temperature process.
• To characterize the optical and performance properties of a-Si:H films and waveguide resonators produced via HiPIMS.
• To assess the potential of this approach for advanced photonic integration, including hybrid and co-packaged optics.

Main Methods:

• Utilized high-power impulse magnetron sputtering (HiPIMS) for depositing a-Si:H films at ultra-low temperatures (70 °C).
• Fabricated a-Si waveguide resonators using the deposited a-Si:H films.
• Characterized the optical properties (refractive index, bandgap) and device performance (Q factor, extinction ratio).

Main Results:

• Achieved high-quality a-Si:H films with a high refractive index (n ≈ 3.52) and a wide optical bandgap (≈ 1.96 eV).
• Demonstrated a-Si waveguide resonators with high quality (Q) factors (~10^5) and extinction ratios (~20 dB).
• The low-temperature deposition process is compatible with integrated silicon photonics and enables low-thermal-budget hybrid integration.

Conclusions:

• Low-temperature HiPIMS is a viable method for fabricating high-performance a-Si:H photonic devices.
• The developed a-Si:H films and devices are suitable for low-loss integrated photonic applications.
• This technique facilitates heterogeneous photonic integration and is a significant step towards co-packaged optics (CPO).