In-Silicon Mietronics for Flatband-Enhanced Upconversion and Interfacial Loss Recovery

Area of Science:

• Materials Science
• Nanotechnology
• Photonics

Background:

• Silicon (Si) photodetectors have limited infrared (IR) responsivity, hindering applications in communication, chemical sensing, and biomedical imaging.
• Lanthanide-doped upconversion nanoparticles (UCNPs) can extend Si spectral response, but weak IR absorption and interfacial losses impede monolithic integration.

Purpose of the Study:

• To overcome limitations of Si photodetectors by enhancing IR responsivity using UCNPs.
• To develop an etch-free monolithic integration platform for UCNP-Si devices.

Main Methods:

• Fabrication of an inverted-index UCNP-Si metasurface using low-index NaYF4:Yb/Er nanocylinders coated with high-index amorphous silicon.
• Utilizing a collective-Mie flatband resonance at 976 nm for enhanced photon absorption and concentration.
• Implementing near-field-mediated passivation to reduce interfacial loss channels.

Main Results:

• Achieved near-unity absorption at 976 nm with a wide numerical aperture (NA ≈ 0.5).
• Demonstrated a record 6800-fold increase in upconversion signal through resonant field enhancement and loss recovery.
• Developed a fully etch-free platform compatible with complementary metal-oxide-semiconductor (CMOS) processing.

Conclusions:

• The UCNP-Si metasurface significantly enhances upconversion efficiency in silicon.
• This platform offers a scalable solution for advanced silicon photodetectors and compact light sources.
• The etch-free integration method is compatible with existing semiconductor manufacturing processes.