Surface illuminated interdigitated Ge-on-Si photodetector with high responsivity

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Photonics

Background:

• Traditional surface-illuminated detectors suffer from low responsivity, limiting their application in sensitive light detection scenarios.
• Germanium-on-silicon (Ge-on-Si) technology offers potential for integrating high-performance photodetectors with silicon electronics.
• Interdigitated electrode structures can influence device performance, including responsivity and bandwidth.

Purpose of the Study:

• To develop a large-size, interdigitated Ge-on-Si photodetector (PD) with improved responsivity for surface illumination.
• To investigate the performance characteristics, including responsivity and bandwidth, of the proposed Ge-on-Si PD.
• To design a Ge-on-Si avalanche photodiode (APD) with an interdigitated structure to suppress dark current noise for weak light detection.

Main Methods:

• Fabrication of a large-size interdigitated "finger-type" Ge-on-Si photodetector.
• Characterization of the photodetector's responsivity and bandwidth under 1550 nm light at room temperature.
• Design of an interdigitated Ge-on-Si avalanche photodiode (APD) to minimize dark current.

Main Results:

• The Ge-on-Si PD achieved a responsivity of approximately 0.64 A/W at 0.5 V under -20 dBm incident power at 1550 nm.
• An optimal bandwidth of 1.537 MHz was achieved with an applied voltage of 3.5 V.
• The designed Ge-on-Si APD exhibits an avalanche voltage of approximately 13.3 V and dark current density in the mA/cm² range.

Conclusions:

• The developed interdigitated Ge-on-Si photodetector demonstrates significantly improved responsivity for surface illumination.
• The device exhibits promising bandwidth performance suitable for various optical detection applications.
• The proposed Ge-on-Si APD design effectively addresses dark current noise, making it suitable for weak light detection conditions.