Pillar Optical Layer for Low-Reflection Photodetectors
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Solution Overview
Problem
Light reflection occurs at the refractive index boundary surface in photodetectors due to the presence of pillars, which affects the efficiency of light detection.
Innovation Solution
The photodetector incorporates an optical layer with pillars arranged in a plane direction to guide light to the photoelectric conversion section, featuring reflection-suppressing films on pillar surfaces with non-flat portions, varying cross-sectional areas, and refractive index gradients to minimize reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pillars are arranged side by side to guide light to the photoelectric conversion section, then light guidance efficiency is improved, but light reflection at the refractive index boundary surface increases
Solution Approach 1:
The invention converts the harmful light reflection at the refractive index boundary surface into a beneficial effect by intentionally creating a reflection suppressing film with a gradient refractive index. The film transforms the abrupt refractive index change into a gradual transition, converting potential reflection losses into enhanced light transmission to the photoelectric conversion section.
Solution Approach 2:
The invention changes the refractive index parameter of the reflection suppressing film from a constant value to a gradient distribution. By varying the refractive index continuously from the pillar material refractive index to the surrounding medium refractive index, the film reduces light reflection at the boundary surface while maintaining effective light guidance to the photoelectric conversion section.
2Object-generated harmful factors
If a reflection suppressing film is provided on the pillar surface, then light reflection is reduced, but the device structure becomes more complex
Solution Approach 1:
The invention achieves reflection suppression by changing the refractive index parameter distribution within the film rather than adding multiple discrete layers. The gradient refractive index profile is formed by controlled material composition variation, simplifying the structure compared to traditional multi-layer anti-reflection coatings while maintaining effective reflection reduction.
Solution Approach 2:
The reflection suppressing film is formed as a composite material structure with gradually varying composition. By combining different materials with different refractive indices in a gradient distribution, the film achieves both reflection suppression and structural integration with the pillar, avoiding the need for separate complex multi-layer structures.
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 reduces light reflection, enhancing the photodetector's efficiency by guiding incident light more effectively to the photoelectric conversion section.
Implementation Method 1
the reflection suppressing film has a non-flat portion including at least one of a recess and a protrusion... and the reflection suppressing film has a refractive index gradient to approach a refractive index of the pillar toward the pillar
Implementation Method 2
Since the refractive index boundary surface exists in the pillar and its peripheral structure, light reflection becomes a problem
Implementation Method 3
a plurality of pillars arranged side by side in a plane direction of a layer to guide at least light to be detected among incident light to the photoelectric conversion section
Implementation Method 4
a photoelectric conversion section
Data Source
AI summary
A photodetector includes: a photoelectric conversion section; and an optical layer provided to cover the photoelectric conversion section, in which the optical layer includes: a plurality of pillars arranged side by side in a plane direction of a layer to guide at least light to be detected among incident light to the photoelectric conversion section; and a reflection suppressing film provided on at least one of an upper surface and a lower surface of the pillar, and the reflection suppressing film has a non-flat portion including at least one of a recess and a protrusion.