Controlled Generation of a p-n Junction in a Waveguide Integrated Graphene Photodetector

Area of Science:

• Photonics and Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Graphene exhibits tunable light absorption and ultrafast photoresponse, making it suitable for high-speed photonics.
• Previous research extensively studied photosignal generation in graphene photodetectors.
• Efficient light conversion at graphene p-n junctions remains a challenge for high-performance devices.

Purpose of the Study:

• To develop a high-performance graphene photodetector integrated on a silicon slot-waveguide.
• To create a graphene p-n junction using a dual-gate mechanism within the optical absorption region.
• To investigate and enhance light conversion efficiency in graphene p-n junctions for optoelectronic applications.

Main Methods:

• Integration of a graphene photodetector onto a silicon slot-waveguide.
• Utilizing the silicon slot-waveguide as a dual gate to form a graphene p-n junction.
• Characterization of photodetector performance under zero bias and biased configurations.

Main Results:

• The photodetector demonstrates dual photoresponse mechanisms: photothermoelectric effect at zero bias and an additional photoconductive contribution under bias.
• Achieved extrinsic responsivities of 35 mA/W (3.5 V/W) at zero bias and 76 mA/W at 300 mV bias voltage.
• The device exhibits a 3 dB bandwidth of 65 GHz, the highest reported for a graphene-based photodetector.

Conclusions:

• The integrated silicon slot-waveguide effectively creates a graphene p-n junction for efficient light detection.
• The dual-gate approach enables tunable photoresponse mechanisms, optimizing device performance.
• This work establishes a new benchmark for graphene photodetectors, paving the way for advanced high-speed chip-integrated photonic systems.