High bandwidth, high responsivity waveguide-coupled germanium p-i-n photodiode

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Photonics

Background:

• Germanium (Ge) p-i-n photodiodes are critical components in optical communication systems.
• Achieving high bandwidth and high responsivity simultaneously in Ge photodiodes presents a significant challenge.
• Existing designs often face trade-offs between speed, sensitivity, and dark current.

Purpose of the Study:

• To demonstrate a novel waveguide-coupled germanium p-i-n photodiode.
• To achieve high responsivity combined with very high -3 dB bandwidth.
• To investigate the impact of a new low-loss contact scheme on photodiode performance.

Main Methods:

• Fabrication of a waveguide-coupled germanium p-i-n photodiode.
• Characterization of photodiode performance, including responsivity, bandwidth, and dark current.
• Utilized a new, low-loss contact scheme to improve device efficiency and reduce carrier diffusion effects.

Main Results:

• Achieved a -3 dB bandwidth of 40 GHz at zero bias and over 70 GHz at -1 V.
• Demonstrated responsivity at 1.55 µm wavelength ranging from 0.84 A/W (zero bias) to 1 A/W (-1 V).
• Measured room temperature dark current density of approximately 1 A/cm² at -1 V.

Conclusions:

• The novel waveguide-coupled germanium photodiode successfully integrates high responsivity with ultra-high bandwidth.
• The implemented low-loss contact scheme is key to achieving superior performance by enhancing responsivity and mitigating bandwidth limitations.
• This device represents a significant advancement for high-speed optical receiver applications.