Avalanche Photodiode Array Layout for High-Aperture Light Detection
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Solution Overview
Problem
Current LiDAR systems with 2D sensors have a low aperture ratio due to insensitive regions, leading to decreased reliability and sensitivity, especially in applications requiring high-resolution long-distance object detection.
Innovation Solution
The design incorporates a 2D sensor with avalanche photodiodes surrounded by trench portions and deep well regions, optimizing the arrangement of transistors and diodes to increase the aperture ratio and reduce optical crosstalk, allowing for a higher sensitivity and reliability in detecting target objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If avalanche photodiodes are arranged in a 2D sensor array, then detection coverage is improved, but aperture ratio decreases due to insensitive regions
Solution Approach 1:
The patent extracts and removes the trench portions (insensitive regions) from the light-receiving surface by designing the avalanche photodiodes to extend beyond the trench boundaries. This extraction eliminates the blocking effect of trenches, allowing light to reach the photodiode active areas more effectively while maintaining the 2D array configuration for comprehensive detection coverage.
Solution Approach 2:
The patent transitions from a planar 2D arrangement to a three-dimensional structure by forming the avalanche photodiodes with depth that extends below the trench portions. This vertical dimensionality change allows the photodiodes to capture light that would otherwise be blocked by the trench structures, effectively increasing the aperture ratio while preserving the 2D sensor array's detection coverage.
2Object-generated harmful factors
If trench portions are used to isolate avalanche photodiodes, then optical crosstalk is reduced, but aperture ratio and sensitivity decrease
Solution Approach 1:
The patent introduces a novel intermediary structure where the avalanche photodiodes themselves act as the primary isolation mechanism rather than relying on trench portions. The photodiodes are designed with extended regions that overlap or come into close proximity, allowing light to reach them while the electrical isolation and depth configuration prevent optical crosstalk between adjacent photodiodes, thus eliminating the need for deep trenches that would block light.
Solution Approach 2:
The patent changes the critical parameter of photodiode depth and spatial arrangement, extending the avalanche photodiodes below the trench portions and optimizing their dimensional parameters. This parameter change allows the system to achieve both optical isolation (reducing crosstalk) and high light sensitivity by capturing photons that would otherwise be blocked by traditional trench structures.
3Object-generated harmful factors
If deep well regions are formed to reduce crosstalk, then optical isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the functions of optical isolation and light detection into a single integrated structure. The avalanche photodiodes are designed to perform both detection and isolation functions simultaneously, eliminating the need for separate deep well regions. This merging reduces manufacturing steps while achieving the desired optical isolation effect through the photodiodes' extended geometry and electrical configuration.
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 improved aperture ratio enhances the sensitivity and reliability of the LiDAR system, reducing optical crosstalk and power consumption while maintaining high-resolution object detection capabilities.
Implementation Method 1
a plurality of avalanche photodiodes provided above the substrate... each of the plurality of avalanche photodiodes surrounded by a trench portion
Implementation Method 2
a microlens array provided to cover the avalanche photodiodes
Data Source
AI summary
A light detector according to one embodiment includes a substrate, a plurality of avalanche photodiodes, a well region, and a microlens array. The plurality of avalanche photodiodes are provided above the substrate. Each of the avalanche photodiodes is surrounded by a trench portion among a plurality of trench portions. The well region is provided between the trench portions that are adjacent to each other. The well region includes at least one of a transistor and a diode. The microlens array is provided to cover the avalanche photodiodes.