Compound Semiconductor Pixel Structure for Low-Crosstalk Imaging
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Solution Overview
Problem
Infrared image sensors face challenges with crosstalk due to the lack of pixel separation structures, leading to reduced sensitivity and increased dark current when using groove-separated pixels with insulating layers.
Innovation Solution
A photoelectric conversion element with a stacked structure of compound semiconductor layers, including a first semiconductor layer, a second semiconductor layer with a larger band gap, and a third semiconductor layer, along with diffusion layers and electrodes, arranged across multiple pixel regions to suppress crosstalk while maintaining sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pixels are separated by a groove formed of an insulating layer, then crosstalk is suppressed, but dark current is easily generated near the interface with the insulating layer and sensitivity may decrease
Solution Approach 1:
The invention extracts and removes the insulating layer groove structure from the photoelectric conversion element. Instead of using grooves filled with insulating material to separate pixels, the patent employs a planar pixel separation structure where pixels are adjacent to each other without intervening insulating layers, thereby eliminating the source of dark current generation at insulating layer interfaces while maintaining crosstalk suppression through alternative means
Solution Approach 2:
The invention segments the pixel separation function from the insulating layer groove structure. Rather than relying on physical grooves filled with insulating material, the patent implements pixel separation through the pixel separation structure defined by the arrangement of photoelectric conversion units and their associated electrodes, separating pixels without introducing harmful insulating interfaces
2Object-affected harmful factors
If pixels are separated by a groove, then crosstalk can be suppressed, but the photoelectric conversion region becomes narrow and sensitivity may decrease
Solution Approach 1:
The invention extracts and eliminates the groove structure that reduces the photoelectric conversion region. By removing the grooves entirely and adopting a planar configuration where pixels are adjacent without physical separations, the photoelectric conversion region is maximized across the entire surface, thereby improving sensitivity while maintaining crosstalk suppression through the pixel separation structure
Solution Approach 2:
The invention transitions from a three-dimensional groove structure to a two-dimensional planar pixel separation approach. Instead of using vertical grooves that reduce the active photoelectric conversion area, the patent implements pixel separation in the horizontal plane through the arrangement of photoelectric conversion units and electrodes, maintaining full surface utilization for photoelectric conversion
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 effectively suppresses crosstalk and dark current, enhancing sensitivity by allowing efficient charge collection across the entire photoelectric conversion area without the need for pixel separation structures.
Implementation Method 1
a second semiconductor layer of a first conductivity type containing a compound semiconductor material having a larger band gap than the first semiconductor layer and stacked on a side of the first semiconductor layer opposite to the light incidence surface
Implementation Method 2
a third semiconductor layer of a first conductivity type containing a compound semiconductor material having a larger band gap than the first semiconductor layer and stacked on the light incidence surface side of the first semiconductor layer
Implementation Method 3
a first diffusion layer of a second conductivity type disposed to penetrate the second semiconductor layer from a side of the second semiconductor layer opposite to the light incidence surface and extend into the first semiconductor layer
Implementation Method 4
a first semiconductor layer of a first conductivity type containing a compound semiconductor material... photoelectric conversion is not performed in the groove region
Data Source
AI summary
[Object] To suppress crosstalk without reducing sensitivity.[Solution] A photoelectric conversion element includes: a first semiconductor layer of a first conductivity type containing a compound semiconductor material; a second semiconductor layer of a first conductivity type containing a compound semiconductor material having a larger band gap than the first semiconductor layer and stacked on a side of the first semiconductor layer opposite to the light incidence surface; a third semiconductor layer of a first conductivity type containing a compound semiconductor material having a larger band gap than the first semiconductor layer and stacked on the light incidence surface side of the first semiconductor layer; a first diffusion layer of a second conductivity type disposed to penetrate the second semiconductor layer from a side of the second semiconductor layer opposite to the light incidence surface and extend into the first semiconductor layer; a first electrode in contact with the first diffusion layer on the side of the second semiconductor layer opposite to the light incidence surface; a second diffusion layer of a second conductivity type disposed in a depth direction of the third semiconductor layer from a light incidence surface side of the third semiconductor layer; a second electrode in contact with the second diffusion layer on the light incidence surface side of the third semiconductor layer; and an insulating layer disposed between the second electrode and the third semiconductor layer.