CQD-on-SiPM Microcell Imaging for Low-Light Photon Detection
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Solution Overview
Problem
Converting charge generation events from individual photons into detectable currents is challenging, especially in low-light conditions, and silicon photomultiplier (SiPM) approaches are inadequate in many instances.
Innovation Solution
An imaging circuitry arrangement is employed that includes a colloidal quantum dot (CQD) layer over an array of SiPM microcells, with separate biases applied to the CQD layer and microcell array, enhancing photon detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon photomultiplier (SiPM) approach is employed to detect photons, then the device can generate imagery from received photons, but the photon detection efficiency remains insufficient in low-light conditions
Solution Approach 1:
The patent combines colloidal quantum dots with silicon photomultiplier microcells to create a composite detection system. The CQD layer is deposited over the SiPM microcell array, forming a hybrid structure that leverages the high quantum efficiency of CQDs in the SWIR spectrum while maintaining the signal amplification capabilities of SiPMs. This composite approach resolves the contradiction by achieving superior photon detection efficiency without requiring a completely new device architecture.
Solution Approach 2:
The colloidal quantum dot layer acts as an intermediary between incoming photons and the silicon photomultiplier microcells. The CQDs absorb photons in the SWIR spectrum and generate charge carriers that are then detected and amplified by the SiPM microcells. This intermediary layer enables efficient photon-to-charge conversion while allowing the existing SiPM technology to perform its signal amplification function, thereby improving detection efficiency without excessive complexity.
2Reliability
If separate biases are applied to the CQD layer and microcell array to enhance detection efficiency, then photon detection efficiency increases, but the circuit complexity increases
Solution Approach 1:
The patent segments the biasing system into two independent parts: a first bias for the CQD layer and a second bias for the SiPM microcell array. This segmentation allows each component to be optimized independently - the CQD layer bias is set below the breakdown voltage to prevent avalanche multiplication, while the SiPM microcells are biased above breakdown voltage for Geiger mode operation. The independent biasing circuits simplify the overall design compared to a single complex biasing system, as each bias circuit can be independently optimized and controlled.
Solution Approach 2:
Different bias conditions are applied to different parts of the detection system according to their specific requirements. The CQD layer receives a lower bias suitable for charge generation without avalanche, while the SiPM microcells receive a higher bias optimized for Geiger mode operation. This localized optimization of bias conditions improves overall detection efficiency while keeping each biasing circuit relatively simple and tailored to its specific function.
3Reliability
If the CQD layer is used to convert photons to charge in the SWIR spectrum, then detection capability in low-light conditions improves, but the manufacturing complexity increases
Solution Approach 1:
The colloidal quantum dots are applied as a colloidal suspension that can be deposited using simple coating techniques. The CQDs self-assemble into a functional layer on the SiPM microcell array, leveraging their colloidal nature to simplify the manufacturing process. This self-organizing property of colloidal quantum dots reduces the complexity of integrating the SWIR detection layer compared to epitaxial growth or other complex thin-film deposition methods.
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
Significantly increases photon detection efficiency, particularly in low-light conditions, enabling applications such as lidar, medical imaging, and night vision by amplifying charge generation events effectively.
Implementation Method 1
Each photon results in a single charge generation event (e.g., an electron or a hole)
Implementation Method 2
A silicon photomultiplier (SiPM) approach can be employed
Data Source
AI summary
The technology employs colloidal quantum dots (CQDs), in which a CQD layer is arranged over an array of SiPM microcells of an image sensor for an imaging module. Separate biases are applied to the CQD layer and to the microcell array. A method includes biasing the CQD layer of an imaging module at a first voltage, and biasing an array of photomultiplier microcells at a second voltage. Upon receiving a photon, the CQD layer generates a charge in response. The charge moves from the CQD layer into the array, where at least one photomultiplier microcell amplifies the charge. A signal from the imaging module is then output according to the amplified charge. This approach can significantly increase photon detection efficiency of an imaging element, which can be employed in a wide variety of applications such as lidar, medical imaging, and night vision or for other low-light imaging situations.