Radiation Detector Guard Rings with Extended Conductive Layers
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Solution Overview
Problem
Radiation detectors face challenges in achieving high spatial resolution while maintaining efficient radiation absorption, particularly in semiconductor detectors where the conversion of radiation into electric signals is direct but can be affected by dark current and avalanche breakdown.
Innovation Solution
The use of multiple guard rings surrounding pixels in a semiconductor radiation detector, with conductive layers extending further than the doped semiconductor regions, helps reduce dark current and delay avalanche breakdown, allowing for improved radiation particle counting and energy measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If semiconductor radiation detectors are used for direct conversion of radiation into electric signals, then spatial resolution is improved, but dark current and avalanche breakdown affect measurement precision
Solution Approach 1:
The detector is segmented into multiple functional regions including pixel regions for radiation detection and guard ring regions for electrical isolation. The guard rings are divided into multiple concentric rings with different doping types and extensions, creating distinct zones that segment the electrical fields and isolate charge carrier paths, thereby reducing dark current and preventing avalanche breakdown while maintaining spatial resolution.
Solution Approach 2:
Guard rings serve as intermediary structures between the pixel regions and the detector periphery. These intermediary doped regions with extended conductive layers act as buffer zones that intercept and control electrical fields, preventing direct interaction between high-field regions and peripheral structures, thus reducing dark current and avalanche effects while preserving the primary detection function.
2Reliability
If the conductive layer extends further than the doped semiconductor region in guard rings, then dark current is reduced and avalanche breakdown is delayed, but device complexity increases
Solution Approach 1:
The guard ring structure utilizes parameter changes in the form of varying conductive layer extensions across different rings. The first, second, and third guard rings have progressively different extension lengths beyond their respective doped regions, creating a gradient structure. This parameter variation optimizes electrical field distribution and charge carrier collection efficiency, reducing dark current and delaying avalanche breakdown while maintaining a systematic rather than arbitrary complexity.
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 configuration enhances the detector's ability to accurately count and measure radiation particle energy by minimizing noise and increasing the stability of the electric field, thereby improving the overall performance and reliability of the radiation detection system.
Implementation Method 1
Semiconductor radiation detectors largely overcome this problem by direct conversion of radiation into electric signals. A semiconductor radiation detector may include a semiconductor layer that absorbs radiation in wavelengths of interest. When a radiation particle is absorbed in the semiconductor layer, multiple charge carriers (e.g., electrons and holes) are generated and swept under an electric field towards electric contacts on the semiconductor layer.
Implementation Method 2
The use of multiple guard rings surrounding pixels in a semiconductor radiation detector, with conductive layers extending further than the doped semiconductor regions, helps reduce dark current and delay avalanche breakdown
Data Source
Figure 1
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Figure 2B
AI summary
A detector has a pixel in a substrate and configured to detect radiation particles incident thereon; a first guard ring in the substrate, surrounding the pixel, and comprising a first doped semiconductor region in the substrate and a first electrically conductive layer in electrical contact to the first doped semiconductor region; a second guard ring in the substrate, surrounding the first guard ring, and comprising a second doped semiconductor region in the substrate and a second electrically conductive layer in electrical contact to the second doped semiconductor region. The first electrically conductive layer overhangs the first doped semiconductor region toward an interior of the first guard ring by a greater extent than the second electrically conductive layer overhangs the second doped semiconductor region toward an interior of the second guard ring.