Tapered Charge Transfer Channel for Photodetection
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Solution Overview
Problem
Current photodetection devices face limitations in achieving high temporal resolution for detecting the timing of incident light due to charge density dispersion as charges travel further from the photoelectric conversion unit.
Innovation Solution
The device incorporates a first charge transfer channel with a tapered shape, where the width at the photoelectric conversion unit side is greater than at the far end, creating a stronger electric field that suppresses charge dispersion, and includes multiple charge transfer and accumulation channels with gate electrodes that control charge transfer and cutoff, enhancing temporal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge is transferred through a long charge transfer channel from the photoelectric conversion unit, then charge can reach the accumulation channels, but charge density disperses and temporal resolution deteriorates
Solution Approach 1:
The charge transfer channel is designed with a tapered cross-sectional area that is larger near the photoelectric conversion unit and smaller toward the accumulation channels. This local variation in geometry creates a corresponding variation in electric field strength, with stronger fields near the conversion unit that suppress charge dispersion, while maintaining adequate field strength throughout the transfer path.
Solution Approach 2:
The patent changes the physical parameter of the charge transfer channel (cross-sectional area) along its length, creating a tapered structure. This parameter change results in a gradient electric field distribution that optimizes charge transport by providing stronger confinement where needed (near the conversion unit) while still enabling efficient transfer to the accumulation channels.
2Measurement precision
If multiple charge accumulation channels are provided to detect different timing positions, then temporal resolution can be improved, but device complexity increases
Solution Approach 1:
The detection function is segmented into multiple discrete timing positions, with each accumulation channel corresponding to a specific time window. Charges are transferred to different accumulation channels based on their arrival time, enabling temporal resolution through spatial segmentation of the detection function.
Solution Approach 2:
The tapered charge transfer channel serves multiple functions simultaneously: it transports charges over distance, suppresses charge dispersion through its gradient electric field, and enables timing resolution by directing charges to different accumulation channels. This multi-functionality reduces the need for separate dedicated structures for each function.
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 effectively improves temporal resolution by minimizing charge dispersion, allowing for more accurate detection of light incidence timing.
Implementation Method 1
a photoelectric converter that generates charge
Implementation Method 2
creating a stronger electric field that suppresses charge dispersion
Data Source
AI summary
A photodetection device includes: a photoelectric converter generating charge; a first channel having first and second ends, the first end being connected to the photoelectric converter, charge being transferred from the first end toward the second end; a second channel diverging from the first channel at a first position of the first channel; a third channel diverging from the first channel at a second position of the first channel; a first accumulator accumulating charge transferred from the first channel through the second channel; a second accumulator accumulating charge transferred from the first channel through the third channel; and at least one first gate electrode switching between transfer/cutoff of charge in the second channel, and switching between transfer/cutoff of charge in the third channel, a width of the first channel at the first end being greater than a width of the first channel at the second end in a plan view.