CMOS Avalanche Photon Sensor Array With Quenching and Crosstalk Isolation
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Solution Overview
Problem
Conventional photodetection technologies for low photon fluxes, such as PMTs and SPADs, face challenges including large size, high voltage bias, sensitivity to magnetic fields, high costs, and poor signal-to-noise ratios, limiting their effectiveness in applications like medical imaging and homeland security.
Innovation Solution
A breakdown-avalanche photon sensor array with a quenching element, implemented in CMOS technology, which operates in Geiger-mode to achieve high sensitivity for single photon detection by utilizing a semiconductor substrate and epitaxial layer with a pn-junction and quenching element, suppressing optical crosstalk with trenches and guard rings to enhance accuracy and reduce production complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional photomultiplier tubes (PMT) and hybrid photon detectors (HPD) are used for low photon flux detection, then high sensitivity and low dark current are achieved, but device size becomes large, voltage bias becomes high, and manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical vacuum tube structure of conventional PMTs with a solid-state semiconductor device structure. The photomultiplier tube's vacuum envelope, dynodes, and electron multiplication structure are substituted with a semiconductor substrate containing a pn-junction and avalanche region, eliminating the need for vacuum sealing and complex mechanical assembly while maintaining photon detection capability.
Solution Approach 2:
The patent changes the operating parameters from the high voltage bias (typically 1000V or more) required by conventional PMTs to a lower voltage regime suitable for semiconductor operation. The avalanche multiplication is achieved through controlled electric field breakdown in the semiconductor depletion region rather than through cascaded dynode multiplication, enabling operation at reduced voltage levels.
2Measurement precision
If conventional photomultiplier tubes (PMT) are used for low photon flux detection, then high sensitivity is achieved, but sensitivity to ambient magnetic fields increases and device complexity increases
Solution Approach 1:
The patent replaces the vacuum tube electron multiplication mechanism with a solid-state avalanche multiplication process. The electron cloud dynamics and magnetic field interactions inherent in PMT operation are substituted with carrier multiplication through impact ionization in the semiconductor depletion region, which is inherently less sensitive to external magnetic fields.
3Measurement precision
If semiconductor avalanche photosensors operate in high-gain avalanche mode with increased bias voltage, then single photon detection capability is achieved, but proportional measurement of photon flux is lost and signal fidelity deteriorates
Solution Approach 1:
The patent divides the semiconductor device into distinct functional regions: a photosensitive region for photon absorption and carrier generation, and a separate avalanche multiplication region for signal amplification. This spatial segmentation allows the device to operate in Geiger mode for single photon detection while preserving the ability to maintain proportional response characteristics through controlled electric field distribution across the different regions.
4Measurement precision
If breakdown-avalanche photon sensors operate in Geiger mode with high amplification gain, then single photon sensitivity is achieved, but dark current events cannot be distinguished from photon signals and signal-to-noise ratio deteriorates
Solution Approach 1:
The patent implements dynamic control of the electric field in the avalanche region through time-varying bias voltage application. The electric field strength is modulated to distinguish between genuine photon-induced avalanches and dark current events based on their different temporal characteristics and amplitude profiles, enabling discrimination capability while maintaining single photon sensitivity.
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 enables high sensitivity and accuracy in detecting low photon fluxes with reduced production costs and complexity, improving signal-to-noise ratios and operational stability, suitable for applications like medical imaging and homeland security.
Implementation Method 1
A photon absorbed in the breakdown-avalanche sensor generates an electron-hole pair
Implementation Method 2
the loss of proportional measurements of the photon flux, since the electrical signal generated by the avalanche discharge
Data Source
AI summary
A breakdown-avalanche photon sensors array (10) is shown, which is implemented in CMOS technology, wherein the breakdown-avalanche photon sensors array (10) has single photon sensitivity, comprising: a semiconductor substrate (11); and an epitaxial layer (12), which is located above the semiconductor substrate (11); and a breakdown-avalanche photon sensor (13), which is located within the epitaxial layer (12), wherein the breakdown avalanche photon sensor (13) comprises: a guard ring (3) and a quenching element (5), which is electrically connected to the breakdown-avalanche photon sensor (13), wherein the quenching element (5) is configured for quenching the breakdown-avalanche photon sensor (13) after detection of a photon. Furthermore, a digital breakdown-avalanche photon sensor (11), a digital breakdown-avalanche photon sensors array (20)and an digital photomultiplier imager (40) are shown.