Imaging Device Blocking Layer for Pixel Miniaturization and Low Dark Current
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Solution Overview
Problem
Existing imaging devices face challenges in achieving miniaturization of pixels while maintaining image quality and suppressing dark currents due to limitations in transistor reduction and photoelectric conversion layer configurations.
Innovation Solution
The imaging device incorporates a photoelectric conversion unit with a blocking layer that has specific energy barriers to prevent minority charge migration, allowing for the removal of a reset transistor and enabling efficient charge accumulation and resetting operations without constant voltage supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the pixel is miniaturized while retaining the size of the transistor, then the pixel size is reduced, but the aperture ratio is reduced and image quality deteriorates
Solution Approach 1:
The invention divides the pixel into two separate functional units: a photoelectric conversion unit (with photodiode and blocking layer) and a signal reading unit (with transistors). This segmentation allows independent optimization of each unit - the photodiode can be maximized for light capture while transistors are minimized for compactness, resolving the contradiction between pixel miniaturization and maintaining aperture ratio.
Solution Approach 2:
The invention introduces a vertical stacking dimension by placing the photoelectric conversion unit and signal reading unit at different vertical levels within the pixel structure. This three-dimensional arrangement allows both units to coexist without lateral overlap, enabling pixel miniaturization while preserving the photodiode area for high aperture ratio.
2Length of moving object
If each transistor is miniaturized into a certain level or smaller, then the pixel size is reduced, but the drive capacity is damaged
Solution Approach 1:
By separating the signal reading unit into distinct transistor components positioned vertically, the invention allows each transistor to be miniaturized independently while maintaining their functional relationships. The segmented layout preserves drive capacity despite reduced individual transistor sizes.
3Object-generated harmful factors
If a blocking layer with high energy barrier is introduced to prevent minority charge migration, then dark current is reduced, but device complexity increases
Solution Approach 1:
The blocking layer acts as an intermediary component between the photodiode and the charge accumulation region. This single intermediate layer effectively blocks minority charge migration and reduces dark current without requiring multiple complex structures, maintaining relative simplicity while achieving the desired effect.
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 achieves low dark current and pixel miniaturization by effectively blocking minority charge migration, enabling global or row-based voltage control for improved sensitivity and reduced voltage range requirements.
Implementation Method 1
a photoelectric conversion layer that is located between the first electrode and the second electrode, and that converts incident light into a signal charge
Implementation Method 2
an energy barrier of the blocking layer against migration of a charge having an opposite polarity to a polarity of the signal charge from the second electrode to the photoelectric conversion layer is larger than or equal to 1.8 eV
Data Source
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AI summary
An imaging device according to one aspect of the present disclosure includes: a photoelectric conversion unit including a first electrode, a second electrode, a photoelectric conversion layer that converts incident light into a signal charge, and a blocking layer; and a charge accumulation unit that is coupled to the second electrode, and that accumulates the signal charge. An energy barrier of the blocking layer against migration of a charge having an opposite polarity to a polarity of the signal charge from the second electrode to the photoelectric conversion layer is larger than or equal to 1.8 eV, and an energy barrier of the blocking layer against migration of the charge from the photoelectric conversion layer to the second electrode is smaller than or equal to 1.6 eV.