Single-Photon Pixel Layout for High Fill Factor and Crosstalk Isolation
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Solution Overview
Problem
Existing single-photon detection pixels and arrays face challenges in achieving a high fill factor and miniaturization while maintaining effective single-photon detection capabilities.
Innovation Solution
The proposed solution involves a single-photon detection pixel design that includes a substrate, a first well, heavily doped regions, and a contact, where the substrate and heavily doped regions have a first conductivity type, and the first well and contact have a second conductivity type. This configuration allows for the formation of depletion regions and the use of guard rings and additional isolation regions to enhance detection efficiency and prevent crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If isolation regions are formed between pixels to prevent crosstalk, then reliability is improved, but device area increases and fill factor decreases
Solution Approach 1:
The guard ring structure is nested within the pixel boundary, with the first guard ring surrounding the avalanche photodiode and the second guard ring surrounding the first guard ring. This nested configuration prevents crosstalk between adjacent pixels while minimizing the area occupied by isolation structures, as the guard rings are contained within the pixel footprint rather than extending between pixels.
Solution Approach 2:
Heavily doped regions are selectively formed at specific locations where crosstalk is most likely to occur, such as at the corners and edges of the avalanche photodiode. This localized doping approach provides effective crosstalk prevention at critical points without requiring extensive isolation regions across the entire pixel structure, thereby maintaining a high fill factor.
2Productivity
If pixel size is reduced for miniaturization, then productivity is improved, but detection precision may deteriorate
Solution Approach 1:
The doping concentration parameter is optimized to achieve effective single-photon detection in a miniaturized structure. Heavily doped regions with specific doping concentrations are formed to create appropriate depletion regions that maintain detection sensitivity despite the reduced pixel size. The breakdown voltage and electric field distribution are also adjusted through parameter optimization to ensure reliable single-photon detection capability.
Solution Approach 2:
Multiple functional regions are nested within the miniaturized pixel structure, with the avalanche photodiode at the center, surrounded by the first guard ring, which is in turn surrounded by the second guard ring. This nested configuration allows all necessary functional elements to be contained within a small pixel footprint while maintaining adequate spacing and isolation to prevent crosstalk and preserve detection precision.
3Measurement precision
If fill factor is increased to improve detection efficiency, then detection precision is improved, but device area increases
Solution Approach 1:
The active detection region is concentrated in the avalanche photodiode with heavily doped regions positioned at critical locations for photon detection. By optimizing the local doping distribution and guard ring placement, the pixel achieves high detection efficiency within a compact area, as the heavily doped regions are placed only where needed for detection and crosstalk prevention rather than uniformly across the entire pixel.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves a higher fill factor and miniaturization of single-photon detection pixels and arrays, leading to improved detection efficiency and reliability while preventing crosstalk between pixels.
Implementation Method 1
A high electric field rapidly accelerates photo-generated electrons toward an anode (+), additional electron-hole pairs are sequentially generated due to impact ionization caused by the accelerated electrons
Implementation Method 2
When an incident photon with sufficient energy to emit an electron reaches such a photodiode, an electron-hole pair (EHP) is generated
Data Source
AI summary
A single-photon detection pixel includes a substrate, a first well provided in the substrate, a pair of heavily doped regions provided on the first well, and a contact provided between the pair of heavily doped regions, wherein the substrate and the pair of heavily doped regions have a first conductivity type, and the first well and the contact have a second conductivity type that is different from the first conductivity type.