Photo-Detection Device Noise Reduction via Segmented Charge Multiplication
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Solution Overview
Problem
Conventional Single-photon Avalanche Diodes (SPADs) face increased noise due to the avalanche multiplication of unnecessary charges, which degrades the accuracy of photon detection over time as the reverse bias voltage is applied for extended periods.
Innovation Solution
A photo-detection device is designed with separate semiconductor regions for charge accumulation and multiplication, where the number of signal charges in the second region is less than in the first, and a charge multiplication unit that transfers and avalanche-multiplies these charges, minimizing noise by controlling the transfer and multiplication process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If generation and avalanche multiplication of signal charges are performed in the same region with a long detection period, then detection sensitivity is improved, but noise increases due to avalanche multiplication of unnecessary charges
Solution Approach 1:
The patent divides the photo-detection device into three distinct semiconductor regions: a first region for charge generation, a second region for charge accumulation, and a third region for avalanche multiplication. This spatial segmentation separates the functions that were previously combined, allowing signal charges to be generated in the first region, accumulated in the second region, and then multiplied in the third region. By separating the generation and multiplication regions, the patent prevents unnecessary charges from being avalanche-multiplied during long detection periods, thus reducing noise while maintaining detection sensitivity.
Solution Approach 2:
The second semiconductor region acts as an intermediary between the first region (charge generation) and the third region (charge multiplication). This intermediate accumulation region temporarily stores signal charges before they are transferred to the multiplication region. The intermediary region allows the system to accumulate charges over long periods without subjecting them to avalanche multiplication during the accumulation phase, thereby preventing noise generation while preserving signal charges for subsequent multiplication and detection.
2Measurement precision
If a reverse bias voltage is applied for a long period to accumulate more signal charges, then detection accuracy is improved, but unnecessary charges are avalanche-multiplied increasing noise
Solution Approach 1:
The patent segments the device into distinct regions with specific functions: the first region generates charges under reverse bias, the second region accumulates charges without avalanche multiplication, and the third region performs multiplication. This segmentation allows the reverse bias voltage to be applied in the first region for extended periods to accumulate signal charges, while the second region provides a safe accumulation zone free from avalanche effects, thus improving detection accuracy without increasing noise.
Solution Approach 2:
The patent extracts the avalanche multiplication function from the charge accumulation process. By placing the multiplication function in a separate third region that is spatially distinct from the accumulation region, the system can accumulate charges for long periods without subjecting them to avalanche multiplication. The multiplication process is extracted and performed only when needed, preventing unnecessary charge multiplication and noise generation during the accumulation phase.
3Measurement precision
If the number of signal charges accumulated is increased, then detection sensitivity is improved, but processing time increases
Solution Approach 1:
The patent segments the charge handling process into three distinct phases occurring in separate regions: generation in the first region, accumulation in the second region, and multiplication in the third region. This segmentation allows each phase to be optimized independently - the second region can accumulate charges at high capacity without the time-consuming avalanche multiplication process, enabling rapid accumulation of large numbers of charges. The multiplication phase is then performed efficiently in the third region, reducing overall processing time while maintaining high detection sensitivity.
Solution Approach 2:
The patent performs preliminary charge accumulation in the second semiconductor region before transferring charges to the multiplication region. This preliminary action allows the system to accumulate a large number of signal charges in advance during the integration period, so that when the transfer to the multiplication region occurs, the charges are already ready for rapid processing. This preliminary accumulation reduces the processing time required for subsequent multiplication and readout operations.
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 the accuracy of photon detection by reducing noise from unnecessary charges and allowing for high sensitivity while maintaining efficient processing times, even during long exposure periods.
Implementation Method 1
A reverse bias voltage above the breakdown voltage is applied to the avalanche diode, and a current is multiplied by avalanche multiplication
Implementation Method 2
a photoelectric conversion unit that generates and accumulates charge pairs in accordance with incident light
Data Source
AI summary
A photo-detection device in one embodiment includes: a first semiconductor region that accumulates a signal charge based on an incident light; a second semiconductor region that is capable of accumulating a signal charge, the number of signal charges that can be accumulated in the second semiconductor region being less than the number of signal charges that can be accumulated in the first semiconductor region; a first gate that transfers the signal charge from the first semiconductor region to the second semiconductor region; and a charge multiplication unit that includes a third semiconductor region and avalanche-multiplies the signal charge transferred from the second semiconductor region to the third semiconductor region.