Tunable Photoelectric Layer Image Sensor for Wider NIR-SWIR Sensing
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Solution Overview
Problem
Conventional silicon-based IR image sensors suffer from low quantum efficiency in the near-infrared region, limited miniaturization, high optical cross-talk, and lack of sensitivity above 1100 nm, while CMOS image sensors with narrow band pass filters face high-angle dependent peak shift and fabrication complexity, limiting their wavelength range and field of view.
Innovation Solution
An image sensor structure incorporating a substrate, readout circuit array, and a photoelectric layer with a tunable spectrum, combined with a filter layer having a specific extinction coefficient-defined wavelength, enhancing absorption efficiency and expanding the sensing wavelength range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an ultra-deep Si-based photodiode is used to enhance absorption efficiency in the NIR region, then quantum efficiency is improved, but fabrication cost increases, optical cross talk between pixels increases, and miniaturization is limited
Solution Approach 1:
The patent changes the material parameter from conventional Si to Ge-based semiconductor material, which has inherently higher absorption coefficient in the NIR region. This material parameter change allows achieving high quantum efficiency without requiring ultra-deep photodiode structures, thereby reducing fabrication complexity and optical cross talk while maintaining miniaturization capability
Solution Approach 2:
The patent employs Ge-based semiconductor material as a composite alternative to conventional Si, leveraging the superior optical properties of Ge in the NIR region. This material substitution resolves the contradiction by providing high absorption efficiency in a more compact structure, avoiding the need for ultra-deep photodiodes and associated complexity
2Ease of manufacture
If Si-based material is used for image sensor, then fabrication is easier, but sensitivity above 1100 nm is lost, limiting SWIR region application
Solution Approach 1:
The patent changes the bandgap parameter of the semiconductor material by using Ge-based materials, which have a smaller bandgap than Si. This enables detection of longer wavelengths in the SWIR region (above 1100 nm) while maintaining compatibility with standard semiconductor fabrication processes, thus resolving the contradiction between fabrication ease and wavelength range coverage
3Manufacturing precision
If an interference-type narrow band pass filter is integrated with CMOS image sensor, then narrow band sensing is achieved, but high-angle dependent peak shift occurs, limiting field of view application
Solution Approach 1:
The patent changes the spectral response parameter of the photoelectric layer by using Ge-based semiconductor material with inherently broad spectral coverage. This eliminates the need for narrow band pass filters and their associated angle-dependent peak shift problems, allowing wide field of view application while maintaining precise wavelength selectivity through the material's intrinsic properties
4Reliability
If conventional image sensor structure is used, then current requirements are met, but applicable wavelength range is limited, preventing performance improvement
Solution Approach 1:
The patent fundamentally changes the material composition parameter from Si-based to Ge-based semiconductor, which shifts the spectral response to cover both NIR and SWIR regions. This material parameter change enables the sensor to meet current performance requirements while simultaneously expanding the applicable wavelength range to include SWIR applications
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 improves quantum efficiency and reduces angle-dependent peak shift, enabling a broader wavelength range and higher image density, thus enhancing the performance and applicability of IR image sensors.
Implementation Method 1
The filter layer has a first spectrum defining a first wavelength... The first point aligns with an extinction coefficient of 0.9. The second point aligns with an extinction coefficient of 0.1
Implementation Method 2
The photoelectric layer has a second spectrum defining a second wavelength... The third point aligns with an extinction coefficient of 0.9. The fourth point aligns with an extinction coefficient of 0.1
Data Source
AI summary
The image sensor structure includes a substrate, a readout circuit array, a photoelectric layer and a filter layer. The filter layer has a first spectrum defining a first wavelength. The photoelectric layer has a second spectrum defining a second wavelength. The second wavelength is longer than the first wavelength. The first wavelength corresponds to a first line passing through a first point and a second point on a curve of the first spectrum of the filter layer. The first point aligns with an extinction coefficient of 0.9. The second point aligns with an extinction coefficient of 0.1. The second wavelength corresponds to a second line passing through a third point and a fourth point on a curve of the second spectrum of the photoelectric layer. The third point aligns with an extinction coefficient of 0.9. The fourth point aligns with an extinction coefficient of 0.1.