Single-Ended SPAD Quenching Circuit with DC Isolation
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Solution Overview
Problem
Dual-ended single photon avalanche diodes (SPADs) have limited sensitivity in the near infrared region, necessitating a solution for enhanced sensitivity in this spectral range.
Innovation Solution
A compact high sensitivity sensing device is achieved by using a single-ended SPAD with an anode not isolated from the substrate, where the SPAD and electrical components are formed on the same substrate, and capacitors are used for DC isolation between high and low voltage domains to maintain device compactness and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual-ended SPAD with isolated anode is used, then the SPAD can operate at high voltage, but the device occupies more area and has limited near infrared sensitivity
Solution Approach 1:
The patent merges the SPAD anode with the substrate by removing the isolation layer, allowing the SPAD and readout circuitry to share the same substrate and be formed in close proximity. This integration reduces the overall device area while maintaining high voltage operation capability through careful circuit design with separate voltage domains.
Solution Approach 2:
The patent introduces vertical stacking of voltage domains, with the high voltage domain containing the SPAD and low voltage domain containing the readout circuitry, separated by DC isolation structures. This three-dimensional arrangement allows compact integration while maintaining the functional separation needed for high voltage operation.
2Reliability
If high supply voltage is applied to the SPAD for near infrared detection, then sensitivity increases, but electrical components are exposed to high voltage which increases device complexity
Solution Approach 1:
The patent segments the electrical circuit into distinct high voltage and low voltage domains, with the SPAD operating in the high voltage domain and readout circuitry in the low voltage domain. DC isolation structures separate these domains, allowing each to be optimized independently for its voltage level while reducing overall device complexity.
Solution Approach 2:
The patent introduces DC isolation structures as intermediary elements between the high voltage SPAD domain and low voltage readout domain. These isolation structures enable voltage level translation and signal transfer while protecting low voltage components from high voltage exposure, simplifying the overall electrical architecture.
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 solution provides increased sensitivity and compactness by allowing high supply voltage to the SPAD while keeping second electrical components in a low voltage domain, effectively enhancing detection capabilities in the near infrared region.
Implementation Method 1
A single photon avalanche diode (SPAD) is a highly sensitive detector that are capable of detecting a single photon
Data Source
AI summary
A sensing device that may include a substrate; a single-ended SPAD; first electrical components; second electrical components; and capacitors. The SPAD, the first electrical components and the second electrical components are formed on the substrate. The SPAD and the first electrical components belong to a high voltage domain of the sensing device. The high voltage domain is configured to receive a high supply voltage that exceeds a breakdown voltage of the SPAD. The second electrical components belong to a low voltage domain of the sensing device. The capacitors are coupled between the low voltage domain and the high voltage domain. The first electrical components and the second electrical components belong to an electrical circuit that is configured to perform quenching of the SPAD.