GmAPD Focal Plane Array Resistors for Optical Overstress Tolerance
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Solution Overview
Problem
Geiger-mode avalanche photodiode (GmAPD) focal plane arrays (FPAs) face saturation or loss of functionality due to high-intensity optical signals, which generate excessively large currents that can damage the sensor or corrupt data, known as optical overstress.
Innovation Solution
The integration of limit resistors within each pixel of the GmAPD FPA, either in the photodiode or the read-out integrated circuit (ROIC) unit cell, to gradually reduce the peak current injected into the ROIC, thereby increasing the optical overstress tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high-intensity optical signals are detected by the GmAPD, then the signal detection capability is improved, but excessively large currents are generated that can damage the sensor or corrupt data
Solution Approach 1:
A current-limiting resistor is introduced as an intermediary element between the GmAPD and the readout circuit. This resistor mediates the harmful effect by limiting the peak current that reaches the readout circuit when high-intensity optical signals are detected, thereby preventing optical overstress while allowing the detection capability to function normally
Solution Approach 2:
The current-limiting resistor is designed with appropriate resistance value to provide beforehand cushioning against potential optical overstress. By pre-configuring this protective element, the system is prepared to handle high-intensity signals without causing damage, cushioning the readout circuit from harmful current spikes before they can occur
2Reliability
If limit resistors are integrated into each pixel to reduce peak current, then the optical overstress tolerance is improved, but the timing jitter performance may be degraded
Solution Approach 1:
The resistance value of the current-limiting resistor is carefully optimized to achieve the right balance. By adjusting this parameter, the system achieves sufficient current limiting to prevent optical overstress while minimizing the impact on timing jitter. The resistance value is selected to be high enough to limit peak current but low enough to maintain acceptable timing performance
3Ease of manufacture
If monolithic integration of limit resistors is implemented in each pixel, then the device complexity is reduced and manufacturing is simplified, but the precision control over current limiting may be compromised
Solution Approach 1:
The resistance values of monolithically integrated resistors are carefully designed and optimized during the fabrication process. By adjusting the resistor dimensions and material properties, precise current limiting characteristics are achieved despite the monolithic integration approach, ensuring that the simplified manufacturing does not compromise current control precision
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 allows for the detection and analysis of high-intensity signals while reducing peak current magnitude, preventing data corruption and potential damage, with a factor-of-ten improvement in optical-overload tolerance without significant degradation in timing jitter performance.
Implementation Method 1
a limit resistor, monolithically integrated in the pixel, to limit a magnitude of a current generated by the GmAPD and injected into the ROIC unit cell
Implementation Method 2
Geiger-mode (Gm) avalanche photodiode (APD) focal plane arrays (FPAs)
Data Source
AI summary
An image sensing device including a Geiger-mode avalanche photodiode (GmAPD), a read out integrated circuit (ROIC), and a limit resistor connected to the GmAPD and the ROIC in series, wherein the ROIC includes an active quenching circuit.