APD Pixel Isolation Structure for Crosstalk and Dark Count Suppression
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Solution Overview
Problem
Avalanche photodiodes (APDs) face issues with crosstalk and dark count rate (DCR) due to light emission in high-electric-field regions and dark current generation at interfaces, which affect their sensitivity and accuracy in detecting single photons.
Innovation Solution
The implementation of a sensor design with a hole accumulation region and an isolation region that penetrates through the substrate, along with an electron accumulation region, to reduce crosstalk and dark current, enhancing the Photon Detection Efficiency (PDE) and suppressing DCR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an isolation region is formed between pixels to reduce crosstalk, then crosstalk is reduced, but dark current is generated at the interface between the insulating film and silicon
Solution Approach 1:
A hole accumulation region is introduced as an intermediary layer between the isolation region and the well region. This hole accumulation region accumulates holes at its interface with the isolation region, forming a potential barrier that prevents dark current generated at the insulating film-silicon interface from reaching the multiplication region, while still allowing the isolation region to block optical crosstalk between pixels.
Solution Approach 2:
The structure is segmented into distinct functional regions: the isolation region for optical isolation, the hole accumulation region for electrical isolation and dark current suppression, and the well region for photon detection. This segmentation allows each region to perform its specific function optimally without interfering with others.
2Measurement precision
If a layer for forming a high-electric-field region is embedded to enhance sensitivity, then sensitivity is enhanced, but light emission in the high-electric-field region causes photons to incident on neighboring pixels
Solution Approach 1:
The pixel structure is segmented with an isolation region that penetrates through the substrate, physically dividing the high-electric-field regions of adjacent pixels. This segmentation confines the light emission from each pixel's multiplication region, preventing photons from reaching neighboring pixels while maintaining the high electric field necessary for sensitivity.
3Object-affected harmful factors
If physical isolation between pixels is implemented by use of an insulating film, then crosstalk is reduced, but dark current is generated at the interface
Solution Approach 1:
The hole accumulation region serves as an intermediary between the insulating film's isolation function and the silicon's detection function. It captures and accumulates holes at the interface with the isolation region, creating a potential barrier that blocks dark current while preserving the optical isolation provided by the insulating film.
Solution Approach 2:
The interface between the insulating film and silicon, which normally generates dark current, is converted into a beneficial hole accumulation region. By intentionally allowing hole accumulation at this interface, the structure transforms the harmful dark current generation site into a useful component that provides electrical isolation and dark current suppression.
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
This configuration effectively reduces crosstalk and dark count rate, improving the sensitivity and accuracy of APDs in detecting single photons by isolating pixels and managing electric fields, thereby enhancing the overall performance of the photodetector.
Implementation Method 1
an avalanche photodiode to convert incident light into electric charge
Implementation Method 2
a hole accumulation region between the isolation region and the well region
Implementation Method 3
an isolation region that isolates the well region from at least a second pixel that is adjacent to the first pixel
Implementation Method 4
an electron accumulation region that accumulates electrons on a side wall of the isolation region
Data Source
AI summary
A sensor includes a first substrate including at least a first pixel. The first pixel includes an avalanche photodiode to convert incident light into electric charge and includes an anode and a cathode. The cathode is in a well region of the first substrate. The first pixel includes an isolation region that isolates the well region from at least a second pixel that is adjacent to the first pixel. The first pixel includes a hole accumulation region between the isolation region and the well region. The hole accumulation region is electrically connected to the anode.