SiPM Microcell Quenching Circuit for Noise Reduction
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Solution Overview
Problem
Current solid-state photomultiplier devices, particularly analog SiPMs, face challenges with high 'Dark Count Rate', 'Afterpulsing', and limited Fill Factor, leading to reduced efficiency and increased noise, which complicates low-intensity light detection in applications like PET imaging.
Innovation Solution
The introduction of a photomultiplier device with a 'Passive Quenching - Active Recharge' (PQAR) method, utilizing reset MOS transistors and capacitors to simultaneously switch interruption components, allowing for efficient quenching and recharge of avalanche photodiodes, thereby inhibiting noisy microcells and reducing 'Afterpulsing', while maintaining a high Fill Factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive quenching circuit with resistor is used in each microcell, then avalanche current is limited and quenching is achieved, but device complexity increases and light sensitive area is reduced
Solution Approach 1:
The device is divided into multiple independent microcells, each with its own interruption component (transistor) that can be independently controlled. This segmentation allows individual quenching of noisy microcells without affecting the entire device, reducing the need for complex global quenching circuits while maintaining reliable avalanche quenching capability in each cell.
Solution Approach 2:
The interruption component (transistor) is extracted as a separate controllable element within each microcell, allowing independent control of the quenching function. This extraction enables selective inhibition of noisy microcells through software control rather than requiring complex passive quenching circuits in every cell, thereby reducing overall device complexity while maintaining reliability.
2Productivity
If more light sensitive microcells are integrated on the substrate, then detection efficiency improves, but Fill Factor is limited due to space occupied by quenching circuits
Solution Approach 1:
The interruption components (transistors) are designed with controllable on/off states, allowing dynamic control of each microcell's operational status. Noisy microcells can be dynamically inhibited without physically removing them from the array, maintaining high Fill Factor while enabling detection efficiency improvement through increased microcell count. The system adapts by selectively activating only healthy microcells.
Solution Approach 2:
The polarization voltage parameter is dynamically adjusted to control the operational state of each microcell. By changing the voltage parameter, the interruption component switches between conducting and blocking states, enabling flexible control over which microcells are active. This parameter-based control allows maximum packing density while maintaining detection efficiency through selective microcell activation.
3Reliability
If reset phase is extended to fully recharge photodiodes, then detection readiness improves, but time resolution deteriorates due to longer recovery time
Solution Approach 1:
The photodiodes are pre-charged to a voltage slightly below the breakdown voltage during the reset phase, preparing them for rapid avalanche initiation when needed. This preliminary charging action reduces the recharge time required after detection, improving time resolution while maintaining detection readiness. The system anticipates the need for rapid response by maintaining photodiodes in a near-ready state.
Solution Approach 2:
The reset phase is implemented as a periodic operation with optimized duration, repeatedly charging photodiodes to the optimal voltage level. By timing the reset operations periodically and adjusting the duration to the minimum required for adequate recharge, the system balances detection readiness with time resolution, ensuring photodiodes are ready for the next detection event without excessive recovery time.
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 approach effectively reduces noise, increases the Fill Factor, and enhances production efficiency by automatically inhibiting noisy microcells and minimizing 'Afterpulsing', resulting in improved detection efficiency and lower production costs.
Implementation Method 1
Each one of said light sensitive microcells comprises a reversely polarized avalanche photodiode that responds independently of the others, emitting an elementary charge packet in the moment when a photon is detected
Implementation Method 2
each one of said light sensitive microcells comprises an interruption component intended to interrupt electrical continuity and connected in series to the corresponding avalanche photodiode
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention is a solid-state photomultiplier device (SiPM) (1) for detecting one or more photons (F), comprising a sensitive surface (2) created on a semiconductor substrate (3), wherein the sensitive surface (2) is defined by a plurality of light sensitive microcells (4) connected to one another in parallel in such a way as to send out a common analog output signal (Sout), each one of the light sensitive microcells (4) comprising an avalanche photodiode (5) interposed between a first electrode (6) and a second electrode (7) suited to supply a reverse polarization voltage to the avalanche photodiode (5). The device is provided, for each one of the light sensitive microcells (4), with an interruption component (8) suited to interrupt electric continuity and interposed between the accumulation terminal (53) that accumulates the avalanche charge of the avalanche photodiode (5) and the first electrode (6). The interruption components (8) of the plurality of light sensitive microcells (4) are configured in such a way as to simultaneously switch over from a state of conduction to a state of inhibition or vice versa.