Anisotropic Interlayer Image Sensor for Low Dark Current
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Solution Overview
Problem
Current image sensors face challenges in achieving high photoelectric conversion efficiency and low dark current, especially in low light levels or in LiDAR systems, where small optical signals are detected, and existing solutions either increase photoelectric conversion efficiency at the cost of dark current or vice versa.
Innovation Solution
Incorporating an interlayer with metallic or semi-metallic material having anisotropic electrical conductivity, such as graphene or WTe2, between photodetection layers to absorb external light and generate additional photocurrent, while adjusting the thickness and doping density to control dark current and photoelectric conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional photodetection layers are used to improve photoelectric conversion efficiency, then photoelectric conversion efficiency is improved, but dark current increases
Solution Approach 1:
A graphene interlayer is introduced between the photodetection layer and the electrode to act as an intermediary. This graphene layer selectively transports photogenerated carriers while blocking dark current, resolving the contradiction between improving photoelectric conversion efficiency and reducing dark current.
Solution Approach 2:
The electrical conductivity of the graphene interlayer is controlled by adjusting its doping level. By changing the doping concentration, the graphene layer's ability to transport photocurrent while blocking dark current is optimized, allowing simultaneous improvement of photoelectric conversion efficiency and reduction of dark current.
2Object-generated harmful factors
If photodetection layers are optimized for low dark current, then dark current is reduced, but photoelectric conversion efficiency decreases
Solution Approach 1:
The graphene interlayer serves as a mediator that enables the photodetection layer to maintain low dark current while the graphene itself provides efficient photocurrent transport, thus achieving both low dark current and high photoelectric conversion efficiency simultaneously.
Solution Approach 2:
The device uses a composite structure combining the photodetection layer with the graphene interlayer. This composite structure leverages the complementary properties of both materials: the photodetection layer generates carriers with low dark current, while the graphene layer efficiently transports these carriers, achieving both low dark current and high photoelectric conversion efficiency.
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 enables image sensors to achieve both high photoelectric conversion efficiency and low dark current, effectively detecting small optical signals in low light environments, enhancing performance in applications like LiDAR systems and 3D sensors.
Implementation Method 1
a plurality of photodetection layers provided between the first and second electrodes to convert incident light into an electrical signal
Implementation Method 2
an interlayer provided between the photodetection layers and including a metallic or semi metallic material having anisotropy in electrical conductivity. The interlayer may have a lower electrical conductivity in a direction substantially perpendicular to the interlayer, compared to an electrical conductivity in a direction substantially parallel to the interlayer
Data Source
AI summary
Example embodiments relate to an image sensor configured to achieve a high photoelectric conversion efficiency and a low dark current. The image sensor includes first and second electrodes, a plurality of photodetection layers provided between the first and second electrodes, and an interlayer provided between the photodetection layers. The photodetection layers convert incident light into an electrical signal and include a semiconductor material. The interlayer includes a metallic or semi metallic material having anisotropy in electrical conductivity.