Quantum Dot Pixel Array for Visible and Infrared Separation
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Solution Overview
Problem
Existing photodiodes are not sensitive to both visible and infrared wavelengths due to the reactivity limitations of silicon, leading to inefficiencies in capturing infrared spectrum data and increased dark current and noise.
Innovation Solution
Incorporating a heterojunction based on quantum dots and an optical element with an interference mirror and optical steering element to separate visible and infrared wavelengths, allowing each pixel to capture specific wavelengths effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If silicon-based photodiodes are used, then visible light detection is achieved, but infrared wavelength sensitivity is lost
Solution Approach 1:
The pixel array is segmented into two distinct types: first pixels with single junctions for visible light detection and second pixels with heterojunctions for infrared detection. This segmentation allows each pixel type to be optimized for its specific wavelength range, resolving the contradiction between visible and infrared sensitivity.
Solution Approach 2:
Different regions of the pixel array are assigned different structural qualities: first pixels use silicon single junctions optimized for visible wavelengths while second pixels use heterojunctions with quantum dots optimized for infrared wavelengths. This local differentiation enables simultaneous optimization for both wavelength ranges across the array.
2Ease of manufacture
If a single junction photodiode is used, then manufacturing simplicity is maintained, but infrared sensitivity is insufficient
Solution Approach 1:
The photodiode array is divided into first pixels using simple single junctions and second pixels using heterojunctions. This segmentation allows the majority of pixels to maintain simple manufacturing while a subset of pixels incorporates the more complex heterojunction structure needed for infrared sensitivity.
Solution Approach 2:
The junction structure parameter is changed from single junction to heterojunction in specific pixels to enable infrared sensitivity. This parameter change is applied selectively to second pixels while first pixels maintain the simpler single junction configuration.
3Reliability
If quantum dots are incorporated into all pixels, then infrared sensitivity is improved, but dark current and noise increase
Solution Approach 1:
Quantum dot heterojunctions are implemented only in second pixels dedicated to infrared detection, while first pixels for visible light detection use simple single junctions. This segmentation confines the potential dark current and noise issues to only the infrared pixels where quantum dots are necessary.
Solution Approach 2:
An optical element with interference mirror acts as an intermediary between the two pixel types, directing infrared wavelengths preferentially to second pixels and visible wavelengths to first pixels. This reduces crosstalk and prevents visible light from triggering false signals in infrared pixels.
4Measurement precision
If color filters are used for visible pixels, then visible light detection is optimized, but infrared wavelength separation is compromised
Solution Approach 1:
The pixel array is segmented into first pixels with color filters for visible light and second pixels without color filters for infrared detection. This segmentation allows color filters to be used where they benefit visible light detection while avoiding their interference with infrared wavelength discrimination.
Solution Approach 2:
Color filters are extracted or removed from second pixels to enable infrared detection. This extraction ensures that infrared wavelengths can reach the quantum dot heterojunctions without being blocked or distorted by color filter materials.
5Adaptability or versatility
If visible and infrared pixels are integrated in the same array, then device versatility is improved, but crosstalk between wavelength channels increases
Solution Approach 1:
An optical element with interference mirror serves as an intermediary between incident light and the pixel array, directing visible wavelengths to first pixels and infrared wavelengths to second pixels. This intermediary function reduces crosstalk by spatially separating the wavelength channels before they reach the pixels.
Solution Approach 2:
Different optical path qualities are provided for different pixel types: first pixels receive light optimized for visible wavelengths while second pixels receive light optimized for infrared wavelengths. This local optimization of optical paths minimizes crosstalk between wavelength channels.
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
Improves external quantum efficiency, reduces crosstalk, and decreases dark current while maintaining simplicity in manufacturing and image reconstruction.
Implementation Method 1
the optical element comprises an interference mirror configured to let through towards the second pixel infrared wavelengths, and to reflect visible wavelengths
Implementation Method 2
the optical element comprises an optical steering element configured to direct infrared wavelengths towards the second pixel, and visible wavelengths towards a pixel different from the second pixel
Implementation Method 3
the second pixel comprises a heterojunction based on quantum dots; the heterojunction is sensitive to infrared wavelengths
Data Source
AI summary
An electronic device includes a first pixel having a single junction and a second pixel having a heterojunction formed by a semiconductor substrate layer in contact with a quantum dot layer. A first filter of a first color, configured to let through wavelengths of the first color and infrared, is arranged vertically in line with the first pixel and at least partially vertically in line with the second pixel. An optical element is interposed between the first filter and the second pixel. The first filter and the optical element operate so that the first pixel receives wavelengths of the first color and the second pixel only receives infrared wavelengths.