Photodetector Separators Guide Signal Charges
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Solution Overview
Problem
Conventional photodetectors face limitations in photon detection efficiency due to the suppression of charge outflow and signal charge intrusion into low electric field regions, which affects the area ratio and sensitivity of avalanche photodiodes.
Innovation Solution
A photodetector design featuring a pixel array with a first and second separator, where the second separator overlaps part of the multiplication region and has a higher impurity concentration than the surrounding area, guiding signal charges effectively into the multiplication region while minimizing electrical influence, thereby enhancing photon detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional photodetector structure is used, then the device complexity is low, but the photon detection efficiency is insufficient due to charge outflow and signal charge intrusion into low electric field regions
Solution Approach 1:
The photodetector structure is segmented into multiple functional regions: a multiplication region with high electric field for charge multiplication, and separate first and second low electric field regions for controlled charge transport. This segmentation prevents charge outflow and signal charge intrusion while maintaining detection efficiency through structured spatial division of functions.
Solution Approach 2:
Different regions of the photodetector are assigned different electrical properties: the multiplication region has high electric field strength for avalanche multiplication, while the first and second low electric field regions have suppressed electric fields to prevent charge loss. This local differentiation of electrical characteristics optimizes both charge multiplication and charge transport control.
2Measurement precision
If the area ratio of avalanche photodiode is increased to improve sensitivity, then the photon detection efficiency improves, but charge outflow and signal charge intrusion into low electric field regions occur
Solution Approach 1:
The photodetector is divided into distinct functional zones: a multiplication region for charge multiplication and separate low electric field regions for charge transport. This segmentation allows the avalanche photodiode area to be maximized for sensitivity while the low electric field regions act as protective barriers to prevent charge outflow and signal charge intrusion, maintaining charge control stability.
Solution Approach 2:
The first and second low electric field regions serve as intermediary zones between the multiplication region and external environments. These intermediary regions with suppressed electric fields prevent direct charge outflow and signal charge intrusion, allowing the avalanche photodiode to operate at full area for maximum sensitivity without compromising charge control reliability.
3Measurement precision
If separators are added to suppress charge outflow and signal charge intrusion, then the photon detection efficiency improves, but the device complexity increases
Solution Approach 1:
The separator functions are merged with the intrinsic low electric field regions formed by the semiconductor layer structure. Rather than adding discrete separator components, the patent utilizes the electric field distribution created by the layered semiconductor structure itself to perform separation functions, thereby improving photon detection efficiency without significantly increasing device complexity.
Solution Approach 2:
The low electric field regions serve multiple functions simultaneously: they act as separators to prevent charge outflow and signal charge intrusion, while also providing controlled charge transport pathways. This multi-functionality reduces the need for additional dedicated separator components, maintaining relatively simple device structure while achieving improved photon detection efficiency.
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 proposed design improves photon detection efficiency by suppressing charge outflow and signal charge intrusion, increasing the area ratio of the avalanche photodiode and reducing variations in multiplication amplitude between pixels.
Implementation Method 1
the first semiconductor layer and the first semiconductor region constitute a multiplication region in which a charge is multiplied by avalanche multiplication
Implementation Method 2
light detection sensitivity is enhanced by multiplying the signal charge generated by photoelectric conversion
Data Source
AI summary
A photodetector includes: a pixel array in which a plurality of pixels are arranged in an array. Each of the plurality of pixels includes: a first semiconductor layer and a second semiconductor layer which are a first conductivity type, the second semiconductor layer located above the first semiconductor layer and having an impurity concentration lower than the impurity concentration of the first semiconductor layer; and a first semiconductor region, of a second conductivity type different from the first conductivity type, which is disposed in the second semiconductor layer and joined to the first semiconductor layer. The first semiconductor layer and the first semiconductor region constitute a multiplication region in which a charge is multiplied by avalanche multiplication. The pixel array includes a first separator of the first conductivity type disposed in the second semiconductor layer and a second separator of the first conductivity type disposed in the first semiconductor layer.