SPAD Pixel Multiplier Layout for Uniform Photon Detection
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Solution Overview
Problem
Fully depleted SPADs face large variations in characteristics such as breakdown voltage, photon detection efficiency, and dead time due to large depletion regions, leading to inconsistent performance across pixels in photodetection devices.
Innovation Solution
A photodetection device with pixels that include multiple multipliers coupled in parallel and series to a photoelectric converter, along with a quench section, which reduces characteristic variations by optimizing the electric field and avalanche probability, and uses a semiconductor substrate with specific impurity regions and ion implantation for improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large depletion region is used in fully depleted SPAD, then high collection efficiency and high avalanche probability are achieved, but large variations among pixels in characteristics including VBD, PDE, and DT occur
Solution Approach 1:
The pixel structure is segmented into distinct functional regions: a photoelectric converter region for photon detection, a transfer path region for electron transport, and a multiplier region for signal amplification. This segmentation allows each region to be independently optimized, with the depletion region confined to specific areas rather than spanning the entire pixel, thereby reducing characteristic variations while maintaining high collection efficiency in the photoelectric converter and high avalanche probability in the multiplier regions
Solution Approach 2:
Different regions of the pixel are assigned different electrical properties and doping concentrations tailored to their specific functions. The photoelectric converter has optimized doping for high quantum efficiency, the transfer path has controlled doping for efficient electron transport, and the multiplier has specific doping profiles for high avalanche probability. This local optimization reduces variations in breakdown voltage and other characteristics across pixels
2Manufacturing precision
If multiple multipliers are coupled in parallel and series to the photoelectric converter, then characteristic variations among pixels are reduced, but device complexity increases
Solution Approach 1:
Multiple multiplier units are combined in a standardized configuration where they are coupled in parallel to the photoelectric converter and then connected in series to the quench section. This merging approach creates a uniform structure across pixels that reduces characteristic variations. The standardized coupling method simplifies the manufacturing process despite the increased number of components, as the same connection pattern is replicated across all pixels
Solution Approach 2:
The multiplier configuration serves multiple functions simultaneously: signal amplification through avalanche multiplication, characteristic uniformity across pixels through standardized coupling, and integrated quenching through the shared quench section. This multi-functionality reduces the need for additional separate components, thereby managing device complexity while achieving characteristic uniformity
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
This configuration enhances photon detection efficiency, reduces wiring capacitance, and minimizes variations among pixels, leading to improved quantum efficiency and reduced jitter and degradation in photon detection efficiency.
Implementation Method 1
Each of the pixels includes a photoelectric converter
Implementation Method 2
a high avalanche probability is achieved owing to an efficient rise of an electric field in the depletion region
Data Source
AI summary
A photodetection device according to an aspect of the present disclosure includes a plurality of pixels arranged two-dimensionally. Each of the pixels includes: a photoelectric converter, a plurality of multipliers coupled in parallel to each other and coupled in series to the photoelectric converter, and a quench section coupled to the plurality of multipliers on a side opposite to a coupling side to the photoelectric converter.