Simulation of a back-side illuminated Ge-on-Si single-photon avalanche diode with a light-trapping structure

Area of Science:

• Optoelectronics
• Semiconductor Devices
• Photonics

Background:

• Germanium-on-silicon single-photon avalanche diodes (SPADs) offer CMOS compatibility for short-wave infrared (SWIR) detection.
• Current Ge-on-Si SPADs face limitations in detection efficiency at 1310 nm and 1550 nm due to device structure.

Purpose of the Study:

• To propose and evaluate a back-side illuminated (BSI) Ge-on-Si SPAD with an integrated light-trapping structure.
• To enhance the single-photon detection efficiency (SPDE) at critical SWIR wavelengths.

Main Methods:

• Utilized finite-difference time-domain (FDTD) and TCAD simulations for nanostructure design optimization.
• Implemented a nano-cone array on the substrate back side and an aluminum reflector on the front side.
• Employed a masked implantation technique to control electric field distribution.

Main Results:

• Achieved SPDEs of 37.7% at 1310 nm and 21.2% at 1550 nm.
• Demonstrated a 61.2% reduction in dark count rate (DCR) at room temperature.
• Projected further DCR suppression at cryogenic temperatures.

Conclusions:

• The proposed BSI Ge-on-Si SPAD with light-trapping significantly improves SWIR photon detection.
• This advancement enables larger SPAD arrays and higher integration for SWIR sensing.
• The optimized device structure is crucial for next-generation SWIR imaging technologies.