Optical Detector Guard Regions for Crosstalk Suppression
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Solution Overview
Problem
Optical detectors, particularly those made of silicon or germanium, exhibit poor quantum efficiency in short wavelength regions such as blue and UV light due to device physics and structure, and optimizing them for improved response in these regions often results in significant crosstalk to adjacent detectors.
Innovation Solution
The optical detector design includes a depleted field region with intrinsic or near-intrinsic material, a charge collection node, and guard regions with higher doping concentrations than the charge collection node, which prevents crosstalk and enhances quantum efficiency in short wavelength regions without compromising longer wavelength response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the detector is optimized for improved response in blue and UV regions, then quantum efficiency in short wavelength regions is improved, but crosstalk to adjacent detectors increases significantly
Solution Approach 1:
The detector structure is segmented into distinct functional regions: an active pixel area for light detection and guard regions for crosstalk suppression. The guard regions are spatially separated from the active area by a depleted field region, creating physical and electrical segmentation that prevents charge carrier diffusion between adjacent pixels while maintaining high quantum efficiency in the active region.
Solution Approach 2:
Different regions of the detector are assigned different doping concentrations to optimize local functions. The active pixel area uses intrinsic or near-intrinsic material with low doping for high quantum efficiency, while the guard regions use higher doping concentrations to create strong electric fields that suppress crosstalk. This local differentiation of material properties resolves the contradiction between sensitivity and isolation.
2Object-generated harmful factors
If guard regions are added to prevent crosstalk, then crosstalk between adjacent detectors is reduced, but device complexity increases
Solution Approach 1:
The guard regions are merged with the pixel structure in a planar configuration, sharing common fabrication processes and electrical connections. The guard regions are formed using the same semiconductor material and doping techniques as the active regions, integrating the crosstalk suppression function into the existing pixel architecture rather than adding separate complex isolation structures.
Solution Approach 2:
A depleted field region acts as an intermediary between the active pixel area and the guard regions. This intermediate layer with moderate doping concentration provides a transition zone that facilitates charge carrier collection in the active area while preventing carrier diffusion into adjacent pixels, simplifying the overall isolation structure.
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 design achieves improved quantum efficiency in blue and UV regions while minimizing crosstalk between adjacent detectors, maintaining or even enhancing longer wavelength response.
Implementation Method 1
a photodiode which detects visible and/or non-visible light and converts it to another signal type, such as a current or a voltage
Implementation Method 2
The guard regions are operable to prevent crosstalk to an adjacent optical detector
Data Source
AI summary
An optical detector includes a detector surface operable to receive light, a depleted field region coupled to the underside of the detector surface, a charge collection node underlying the depleted field region, an active pixel area that includes the portion of the depleted field region above the charge collection node and below the detector surface, and two or more guard regions coupled to the underside of the detector surface and outside of the active pixel area. The depleted field region includes an intrinsic or a near-intrinsic material. The charge collection node has a first width, and the guard regions are separated by a second width that is greater than the first width of the charge collection node. The guard regions are operable to prevent crosstalk to an adjacent optical detector.