High performance waveguide-coupled Ge-on-Si linear mode avalanche photodiodes

Area of Science:

• Photonics and Optoelectronics
• Semiconductor Devices
• Integrated Optics

Background:

• Silicon photonics platforms require efficient and high-speed photodetectors.
• Germanium-on-silicon (Ge-on-Si) technology offers a path for integrating photodiodes with silicon photonics.
• Avalanche photodiodes (APDs) provide internal gain, enhancing sensitivity and speed.

Purpose of the Study:

• To present experimental results for a selective epitaxially grown Ge-on-Si separate absorption and charge multiplication (SACM) integrated waveguide-coupled avalanche photodiode (APD).
• To evaluate the performance of fabricated APDs with varying multiplication regions and charge implant dimensions.
• To demonstrate the compatibility of these APDs with existing silicon photonics platforms.

Main Methods:

• Fabrication of epitaxially grown Ge-on-Si waveguide-coupled linear mode avalanche photodiodes.
• Characterization of illuminated device performance, including high-speed measurements.
• Bit error rate (BER) measurements to assess data transmission quality.

Main Results:

• Achieved a record gain-bandwidth product of 432 GHz for a waveguide-coupled APD operating at 1510 nm.
• Demonstrated BER < 10^-12 across a received optical power range of -18.3 dBm to -12 dBm.
• Obtained open eye diagrams at 13 Gbps pseudo-random data at 1550 nm, confirming high-speed operation.

Conclusions:

• The developed Ge-on-Si SACM APD is a high-performance photodetector suitable for silicon photonics.
• The record gain-bandwidth product and demonstrated BER performance highlight the potential for advanced optical communication systems.
• The device's compatibility with silicon photonics platforms facilitates integration and future development.