Nonvolatile optical phase shift in ferroelectric hafnium zirconium oxide

Area of Science:

• Materials Science
• Photonics
• Electrical Engineering

Background:

• Nonvolatile optical phase shifters are crucial for programmable photonic integrated circuits (PICs).
• Ferroelectric materials like BaTiO₃ offer phase shift capabilities but lack CMOS compatibility.
• Hafnium Zirconium Oxide (Hf_0.5Zr_0.5O₂) is a CMOS-compatible ferroelectric material with unexplored photonic applications.

Purpose of the Study:

• To investigate the optical phase shift properties of ferroelectric Hf_0.5Zr_0.5O₂ for photonic applications.
• To assess the potential of Hf_0.5Zr_0.5O₂ as a nonvolatile phase shifter in silicon photonics.

Main Methods:

• Fabrication of a device utilizing Hf_0.5Zr_0.5O₂.
• Optical characterization at a 1.55 μm wavelength under applied electric fields.
• Analysis of the refractive index change and nonvolatile phase shift behavior.

Main Results:

• Observed a negative change in refractive index in a pristine Hf_0.5Zr_0.5O₂ device at 1.55 μm.
• The nonvolatile phase shift occurred only once in the pristine device, irrespective of electric field direction.
• This non-reversible phase shift is attributed to spontaneous polarization within the Hf_0.5Zr_0.5O₂ film.

Conclusions:

• Ferroelectric Hf_0.5Zr_0.5O₂ can induce an optical phase shift relevant for photonic devices.
• The observed non-reversible, nonvolatile phase shift offers unique characteristics for specific photonic applications.
• Further research is needed to explore and optimize Hf_0.5Zr_0.5O₂ for practical silicon photonic integrated circuits.