Bragg Mirror Deep Trench Isolation for Low-Dark-Current Photodetectors
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Solution Overview
Problem
Conventional deep trench isolation regions in single-photon avalanche diodes provide less than optimal isolation, leading to high dark current, poor low-light sensitivity, and diminished signal-to-noise ratio due to metallic contamination and suboptimal fabrication processes.
Innovation Solution
A deep trench isolation region is formed using a Bragg mirror structure, comprising alternating layers of materials with different refractive indices, which provides enhanced optical and electrical isolation without the need for a metallic reflector core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional deep trench isolation region with a metallic reflector core is used, then optical isolation is provided, but metallic contamination leads to high dark current and poor low-light sensitivity
Solution Approach 1:
The patent removes the metallic reflector core from the deep trench isolation region, extracting the harmful metallic contamination source while maintaining the trench structure for optical isolation. The metallic component is completely eliminated and replaced with a non-metallic alternative.
Solution Approach 2:
The patent changes the material composition parameter of the isolation region from metallic to non-metallic materials. This parameter change eliminates contamination while maintaining or improving the optical isolation function through the trench structure alone.
2Object-affected harmful factors
If a conventional deep trench isolation region with a metallic reflector core is used, then optical isolation is provided, but the signal-to-noise ratio is diminished
Solution Approach 1:
By removing the metallic reflector core, the patent eliminates the source of contamination that degrades signal-to-noise ratio, while the trench structure continues to provide optical isolation and reduce crosstalk between adjacent pixels.
Solution Approach 2:
The patent uses composite non-metallic materials in the isolation region that provide both optical isolation properties and electrical isolation properties, improving signal-to-noise ratio by eliminating metallic contamination while maintaining optical crosstalk reduction.
3Object-affected harmful factors
If alternating layers with different refractive indices are used to form a Bragg mirror, then optical isolation is enhanced, but the device structure becomes more complex
Solution Approach 1:
The patent segments the isolation region into alternating layers of materials with different refractive indices, creating a Bragg mirror structure that enhances optical isolation through constructive interference of reflected light waves at each interface.
Solution Approach 2:
The patent utilizes changes in refractive index parameter across multiple layers to create the Bragg mirror effect, achieving enhanced optical isolation through optical interference principles rather than through complex geometric 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 Bragg mirror deep trench isolation region effectively reduces optical crosstalk and electrical crosstalk, leading to improved sensitivity, reduced dark current, and enhanced signal-to-noise ratio in single-photon avalanche diodes.
Implementation Method 1
a deep trench isolation region that includes a bragg mirror
Implementation Method 2
a first plurality of layers and a second plurality of layers that alternate with the first plurality of layers to define a Bragg mirror
Data Source
AI summary
Structures for a photodetector and methods of forming a structure for a photodetector. The structure includes a semiconductor layer having a p-n junction and a deep trench isolation region extending through the semiconductor layer. The deep trench isolation region includes first layers and second layers that alternate with the first layers to define a Bragg mirror. The first layers contain a first material having a first refractive index, and the second layers contain a second material having a second refractive index that is greater than the first refractive index.