Tunnel Junction Photo Detector for High-Sensitivity Image Sensors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CMOS image sensors face challenges in high-density/high-speed frame image sensing due to limited photoelectric capacity and sensitivity issues, particularly in detecting blue and green light, and complex manufacturing processes for color array sensors.
Innovation Solution
A unit pixel design featuring a tunnel junction photo detector with a floated structure, oxide film, and multiple light-absorbing parts for red, green, and blue light, allowing for efficient electron-hole pair generation and electric current flow, along with a micro lens and light-blocking layers to enhance sensitivity and reduce manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the area of the light-absorbing part is increased to improve photoelectric capacity, then the photoelectric efficiency is improved, but the pixel size increases and manufacturing density decreases
Solution Approach 1:
The patent transitions from a planar light-absorbing structure to a three-dimensional stacked structure with multiple light-absorbing parts at different depths. This vertical dimensionality change allows increasing the effective photoelectric area without expanding the lateral pixel footprint, thereby improving photoelectric capacity while maintaining high manufacturing density.
2Device complexity
If the photo detection area is limited due to transistor arrangement, then device integration is maintained, but photoelectric capacity is insufficient
Solution Approach 1:
The patent resolves the conflict between transistor arrangement and photoelectric capacity by moving the light-absorbing structure into the vertical dimension. Multiple light-absorbing parts are stacked above the transistor plane, allowing the photo detection function to extend vertically rather than laterally, thus maintaining device integration while significantly increasing photoelectric capacity.
3Device complexity
If conventional photo diodes are used, then simple structure is maintained, but electrostatic capacity is small and saturation occurs easily
Solution Approach 1:
The patent merges multiple light-absorbing parts with different wavelength optimization characteristics into a single integrated photo detection unit. This combination allows the photo detector to accumulate electrostatic capacity across multiple stacked elements, increasing total capacity and reducing saturation while maintaining a unified device structure.
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 design achieves high-sensitivity and high-speed frame operation across various illumination levels, enabling efficient photoelectric current generation and self-amplification of signals without additional amplification devices, while simplifying manufacturing and reducing pixel size variations.
Implementation Method 1
Tunneling may occur through the oxide film between at least one of the source and the drain and the light-absorbing part
Implementation Method 2
one electron-hole pair (EHP) is generated for one photon that is incident at a unit pixel light-absorbing part
Implementation Method 3
When light is irradiated to a light-absorbing part inside a unit pixel of an image sensor chip, the image sensor detects the light incident at each unit pixel and the amount of the light and transforms an optical signal to an electrical signal
Data Source
AI summary
A unit pixel of an image sensor and a photo detector are disclosed. The photo detector of the present invention can include: a light-absorbing part configured to absorb light by being formed in a floated structure; an oxide film having one surface thereof being in contact with the light-absorbing part; a source being in contact with one side of the other surface of the oxide film and separated from the light-absorbing part with the oxide film therebetween; a drain facing the source so as to be in contact with the other side of the other surface of the oxide film and separated from the light-absorbing part with the oxide film therebetween; and a channel formed between the source and the drain and configured to form flow of an electric current between the source and drain.