Key Takeaways & Executive Findings
- •• A deep-junction SPAD with a p-implant/HVNW junction enhances NIR sensitivity, achieving a PDP of 6.8% at 905 nm. • Optimizing guard ring design improves fill factor from 20.7% to 39.1% when active diameter increases from 5 to 10 μm, boosting peak PDE from 13.3% to 25.8%. • A field polysilicon gate structure connected to the p+ anode reduces dark count rate by 76.6%. • At 5 V excess bias, the device achieves a low DCR of 2.12 cps/μm2, an afterpulsing probability of 1.2%, and a timing jitter of 216 ps.
Abstract
A high-sensitivity, low-noise single photon avalanche diode (SPAD) detector was presented based on a 180 nm BCD process. The proposed device utilizes a p-implant layer/high-voltage n-well (HVNW) junction to form a deep avalanche multiplication region for near-infrared (NIR) sensitivity enhancement. By optimizing the device size and electric field of the guard ring, the fill factor (FF) is significantly improved, further increasing photon detection efficiency (PDE). To solve the dark noise caused by the increasing active diameter, a field polysilicon gate structure connected to the p+ anode was investigated, effectively suppressing dark count noise by 76.6%. It is experimentally shown that when the active diameter increases from 5 to 10 μm, the FF is significantly improved from 20.7% to 39.1%, and thus the peak PDE also rises from 13.3% to 25.8%. At an excess bias voltage of 5 V, a NIR photon detection probability (PDP) of 6.8% at 905 nm, a dark count rate (DCR) of 2.12 cps/μm2, an afterpulsing probability (AP) of 1.2%, and a timing jitter of 216 ps are achieved, demonstrating excellent single photon detection performance.
1. Introduction
Silicon single-photon avalanche diodes (SPADs), operating in Geiger mode, have emerged as critical components in cutting-edge applications such as biomedical imaging, LiDAR, and quantum communication, owing to their exceptional single-photon sensitivity and timing resolution. However, current SPAD performance necessitates addressing a critical trade-off: enhancing photon detection efficiency (PDE) while suppressing dark count rate (DCR).
To comply with human eye safety, SPAD with NIR sensitivity enhancement should be investigated. PDE is defined as the product of photon detection probability (PDP) and fill factor (FF). Here, PDP represents the ratio of photons detected by the SPAD device to the total incident photons, directly reflecting the comprehensive detection efficiency of the device under practical operating conditions, which is inherently limited by device structures and process conditions.
Many SPAD structures have been investigated in recent years. For instance, conventional FSI (front-side illumination) p+/n-well SPADs in 180 nm CMOS achieve a peak PDP of 48%. However, the DCR of this device is 16 cps/μm2 because the multiplication region is... (text truncated).
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Zhentao Ni, Dajing Bian, Haoxiang Jiang, Xiaoming Huang, Yue Xu (2025). A deep-junction single-photon detector with field polysilicon gate structure for increased photon detection efficiency and reduced dark count noise. SinoTechIntel Verified Research. https://doi.org/10.1088/1674-4926/25060004
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Frequently Asked Questions
What is the main innovation of this SPAD detector?
The main innovation is the integration of a deep p-implant/high-voltage n-well junction for enhanced NIR sensitivity and a field polysilicon gate structure that reduces dark count noise by 76.6%.
How does the field polysilicon gate improve performance?
The field polysilicon gate, connected to the p+ anode, effectively suppresses dark count noise, reducing DCR by 76.6% without compromising photon detection efficiency.
What are the key performance metrics at 5 V excess bias?
At 5 V excess bias, the SPAD achieves a NIR PDP of 6.8% at 905 nm, a DCR of 2.12 cps/μm2, an afterpulsing probability of 1.2%, and a timing jitter of 216 ps.
How does the fill factor change with active diameter?
When the active diameter increases from 5 to 10 μm, the fill factor improves from 20.7% to 39.1%, leading to a peak PDE increase from 13.3% to 25.8%.
What applications can benefit from this SPAD?
This SPAD is suitable for applications requiring high sensitivity in the near-infrared range, such as LiDAR, biomedical imaging, and quantum communication.
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