Horn Antenna Pixel Structure for Low-Leakage IR Sensing
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Solution Overview
Problem
Image sensors for infrared light face challenges in reducing leakage current due to larger Ge-based photosensitive detector areas, which increase interface states at the Ge-dielectric interface, while maintaining detector sensitivity.
Innovation Solution
The design incorporates a horn antenna structure with a smaller surface area on one side and a waveguide structure to direct incoming infrared light onto a Ge-based photosensitive structure, reducing the required Ge surface area and minimizing leakage current, along with a method for fabricating such pixels that includes epitaxial growth and dielectric layer management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a larger Ge-based photosensitive part is used, then detector sensitivity is improved, but leakage current increases due to increased interface states at the Ge-dielectric interface
Solution Approach 1:
The patent introduces a three-dimensional horn antenna structure that tapers from a larger first surface area to a smaller second surface area. This dimensional transition allows the structure to capture infrared light over a larger effective area while confining the Ge-based photosensitive part to a smaller volume, thereby reducing interface states and leakage current while maintaining detection sensitivity.
Solution Approach 2:
The Ge-based photosensitive part is nested within the horn antenna structure, which itself is integrated with the waveguide structure. This nested arrangement allows the photosensitive region to be contained within a reduced volume while still benefiting from the light-collecting advantage of the larger horn antenna opening, effectively decoupling the light collection area from the active detection area.
2Object-generated harmful factors
If the Ge surface area is reduced, then leakage current is reduced, but detector sensitivity may be compromised
Solution Approach 1:
The horn antenna structure serves as an intermediary between the incoming infrared light and the reduced Ge-based photosensitive part. The waveguide structure acts as another intermediary to channel and concentrate the light onto the smaller photosensitive area, enabling the system to maintain sensitivity despite the reduced Ge surface area by efficiently directing light to the active region.
3Productivity
If a horn antenna structure with tapered geometry is implemented, then light directionality and coupling efficiency are improved, but fabrication complexity increases
Solution Approach 1:
The horn antenna structure is segmented into distinct regions: a first surface with larger area, a tapered lateral side, and a second surface with smaller area. This segmentation allows each region to be optimized independently for its specific function (light collection, transition, and coupling), simplifying the overall fabrication process while maintaining the benefits of the tapered geometry.
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 detector sensitivity while reducing leakage current and fabrication costs, contributing to more efficient and environmentally friendly image sensors.
Implementation Method 1
a Ge-based photosensitive structure configured to absorb infrared light and generate a photocurrent in response
Implementation Method 2
the horn antenna structure and the waveguide structure are configured to direct incoming infrared light onto the photosensitive structure
Data Source
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AI summary
An image sensor for sensing infrared light comprises at least one pixel, comprising: a horn antenna structure comprising a first side, a second side and one or more lateral sides connecting the first side and the second side, wherein the first side faces incoming light and wherein a surface area of the second side is smaller than a surface area of the first side, a waveguide structure arranged at the second side of the horn antenna structure, and a Ge-based photosensitive structure configured to absorb infrared light and generate a photocurrent in response, wherein the horn antenna structure and the waveguide structure are configured to direct incoming infra-red light onto the photosensitive structure.