Over 220 GHz evanescently coupled MUTC-PDs with enhanced responsivity

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Photonics

Background:

• High-speed photodetectors are crucial for modern optical communication systems.
• Existing photodetectors often face a trade-off between bandwidth and responsivity.
• Uni-traveling carrier photodiodes (UTC-PDs) offer potential for high-speed operation.

Purpose of the Study:

• To present evanescently coupled waveguide modified uni-traveling carrier photodiodes (MUTC-PDs).
• To achieve ultra-wide bandwidth and high responsivity simultaneously.
• To overcome the conventional trade-off limitations in high-speed photodetectors.

Main Methods:

• Designed a novel epitaxial structure with a multilayer input waveguide for enhanced light absorption.
• Optimized passivation schemes, on-chip matching resistors, and high-impedance coplanar waveguide (CPW) electrodes.
• Fabricated 4 × 5 µm² MUTC-PDs.

Main Results:

• Achieved a record responsivity of 0.56 A/W.
• Demonstrated a 3-dB bandwidth exceeding 220 GHz.
• Showcased clear eye opening for 280 Gb/s PAM4, 330 Gb/s PAM6, and 384 Gb/s PAM8 signals.

Conclusions:

• The developed MUTC-PDs successfully overcome the bandwidth-responsivity trade-off.
• These photodiodes are suitable for next-generation high-speed optical communication systems.
• The novel waveguide structure and optimization techniques contribute to record-breaking performance.