Imaging Device Charge Blocking Layer Impurity Gradient
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Solution Overview
Problem
Existing imaging devices face challenges in improving the signal-to-noise (S/N) ratio during imaging, particularly when two different bias voltages are applied to the photoelectric conversion element, which is necessary for achieving a global shutter function.
Innovation Solution
The imaging device incorporates a photoelectric conversion element with a charge blocking layer containing an impurity, where the concentration of the impurity is higher on the surface facing the photoelectric conversion layer than on the surface facing the pixel electrode. This configuration allows for efficient extraction of signal charges and reduction of noise by controlling the electric field and charge flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a charge blocking layer is used to prevent backflow of charges and improve charge extraction efficiency, then charge extraction efficiency is improved, but the S/N ratio deteriorates due to electron injection and hole backflow
Solution Approach 1:
The charge blocking layer is designed with non-uniform impurity concentration, having a first region with higher impurity concentration and a second region with lower impurity concentration. This local quality variation allows different regions to perform different functions: the high impurity concentration region effectively blocks charge backflow to improve extraction efficiency, while the low impurity concentration region reduces noise by minimizing electron injection and hole backflow.
2Adaptability or versatility
If two different bias voltages are applied to achieve global shutter function, then global shutter function is achieved, but the S/N ratio deteriorates
Solution Approach 1:
The charge blocking layer employs a non-uniform impurity concentration distribution with distinct first and second regions. This local quality differentiation enables the layer to simultaneously support the application of two different bias voltages for global shutter operation while maintaining low noise levels, as the varying impurity concentration optimizes charge blocking performance under different voltage conditions.
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 proposed solution effectively improves the S/N ratio during imaging by reducing the injection of electrons and the backflow of holes, thereby enhancing the charge extraction efficiency and noise reduction in the imaging device.
Implementation Method 1
a photoelectric conversion layer that is located between the pixel electrode and the counter electrode and that generates an electron and a hole
Implementation Method 2
The charge blocking layer contains an impurity and has a first surface facing the photoelectric conversion layer and a second surface facing the pixel electrode. The concentration of the impurity on the first surface is higher than the concentration of the impurity on the second surface
Data Source
AI summary
An imaging device includes a plurality of pixels and a voltage supply circuit. Each of the plurality of pixels includes: a pixel electrode; a counter electrode; a photoelectric conversion layer located between the pixel electrode and the counter electrode; and a charge blocking layer located between the pixel electrode and the photoelectric conversion layer. The charge blocking layer contains an impurity and has a first surface facing the photoelectric conversion layer and a second surface facing the pixel electrode. The concentration of the impurity on the first surface is higher than the concentration of the impurity on the second surface. The voltage supply circuit supplies a first voltage between the counter electrode and the pixel electrode in a first period and supplies a second voltage different from the first voltage between the counter electrode and the pixel electrode in a second period.