Whispering gallery germanium-on-silicon photodetector.

Area of Science:

• Photonics
• Integrated Optics
• Semiconductor Devices

Background:

• Optical communication networks require efficient and compact photodetectors.
• Germanium-on-silicon (Ge-on-Si) photodetectors are crucial for silicon photonics integration.
• Existing photodetectors face challenges in bandwidth, footprint, and wavelength range.

Purpose of the Study:

• To design and demonstrate the first whispering gallery (WG) germanium-on-silicon (Ge-on-Si) photodetector.
• To achieve evanescent coupling from a silicon bus waveguide in a CMOS-compatible process.
• To enable simultaneous wavelength filtering and power detection for high-capacity optical networks.

Main Methods:

• Fabrication of a WG Ge-on-Si photodetector using a CMOS-compatible process.
• Evanescent coupling of light from a silicon bus waveguide to the germanium resonator.
• Characterization of the photodetector's responsivity, dark current, bias voltage, and optoelectric bandwidth.
• Optimization for long-wavelength detection up to 1630 nm.

Main Results:

• Demonstration of the first WG Ge-on-Si photodetector with evanescent coupling.
• Achieved a small footprint (63.6 μm²).
• High responsivity (∼1.04 A/W at 1530 nm) and large optoelectric bandwidth (32.9 GHz).
• Low bias voltage (-1 V) and low dark current (2.03 nA).
• Extended detection range up to 1630 nm with responsivity >0.45 A/W.

Conclusions:

• The developed WG Ge-on-Si photodetector is a significant advancement for optical communication networks.
• Its performance characteristics make it ideal for handling high network data traffic.
• The device serves as a key building block for future integrated photonic systems, enabling wavelength filtering and detection.