Avalanche Photodiode Array Cross Talk Suppression
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Solution Overview
Problem
Densely packed Geiger-mode avalanche photodiode arrays experience significant optical cross talk, leading to false detection events and reduced performance, particularly in high-density arrays used for applications like terrain mapping and deep space communication.
Innovation Solution
The implementation of an avalanche photodiode array design where each photodiode is laterally isolated from others, with a cross talk blocking material region adjacent to the photodiodes that absorbs or reflects secondary photons, preventing them from traveling between photodiodes and eliminating optical cross talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If photodiodes are densely packed to increase array density and reduce size, then array integration and scalability improve, but optical cross talk between photodiodes increases causing false detection events
Solution Approach 1:
The patent divides the photodiode array into laterally isolated units by removing substrate material between adjacent photodiodes, creating physically separated detection elements that prevent cross talk while maintaining high array density
Solution Approach 2:
The patent extracts and removes the substrate material that connects and supports the photodiodes, eliminating the medium through which secondary photons could travel between adjacent photodiodes and cause false detections
2Area of stationary object
If photodiodes are spaced closer together to increase array size and coverage, then imaging resolution and field of view improve, but cross talk intensity increases leading to blurring and potential blinding of the array
Solution Approach 1:
By laterally isolating each photodiode through substrate removal, the patent enables closer spacing without increasing cross talk, as each photodiode operates independently without optical coupling through the substrate
Solution Approach 2:
The patent introduces air gaps (void spaces) between adjacent photodiodes that act as optical isolators, preventing secondary photons from traveling between photodiodes while allowing the photodiodes to be positioned closer together
3Measurement precision
If Geiger-mode operation is used to achieve single-photon detection accuracy, then detection sensitivity improves, but secondary photon emission increases causing more cross talk events
Solution Approach 1:
The patent removes the substrate that would transmit secondary photons between photodiodes, eliminating the harmful effect of secondary photon emission from Geiger-mode operation while preserving the detection sensitivity benefit
Solution Approach 2:
The patent converts the harmful secondary photons generated during Geiger-mode avalanche events into beneficial isolated events by preventing their propagation to neighboring photodiodes, allowing aggressive biasing for maximum detection sensitivity without cross talk penalties
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 design enhances imager performance by allowing increased detection efficiency and sharper feature definition in 3D laser radar images, enabling closer spacing of photodiodes without increased cross talk, and supports a wide range of advanced single-photon detection applications.
Implementation Method 1
a cross talk blocking material region adjacent to the photodiodes that absorbs or reflects secondary photons
Implementation Method 2
a cross talk blocking material region adjacent to the photodiodes that absorbs or reflects secondary photons
Implementation Method 3
the absorption of an incident photon at the APD to produce secondary charges by impact ionization
Implementation Method 4
An APD is operated-under reverse bias conditions that enable the absorption of an incident photon at the APD to produce secondary charges by impact ionization, lending the term 'avalanche'
Data Source
AI summary
There is provided an avalanche photodiode array that includes a plurality of avalanche photodiodes. Each avalanche photodiode in the array includes a stack of active photodiode materials. The stack of active photodiode materials includes a first electrical contact layer, a second electrical contact layer; an absorber material layer and an avalanche material layer each disposed between the first electrical contact layer and the second electrical contact layer; and an optical interface surface to the avalanche photodiode. The optical interface surface consists of an exposed surface of the first electrical contact layer, arranged for incident external radiation to directly enter the first electrical contact layer. Each avalanche photodiode stack of active photodiode materials is laterally isolated from the other avalanche photodiodes in the photodiode array.