Geiger-Mode Avalanche Photodiode Structure for Afterpulsing Control
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Solution Overview
Problem
Geiger-mode avalanche photodiodes (GMAPs) suffer from noise issues due to afterpulsing and delayed crosstalk, which reduce detection efficiency and dynamics, especially in large arrays operating at high biasing voltages, and existing solutions either reduce photodiode size or gain, compromising performance.
Innovation Solution
A Geiger-mode avalanche photodiode design with a semiconductor body structure that includes a substrate, epitaxial layers, and gettering regions to reduce minority carrier lifetime and prevent secondary photon absorption, featuring a PN junction with a guard ring and dielectric regions to manage electrical fields and prevent edge breakdown, while maintaining high sensing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reverse-biasing voltage is increased above breakdown voltage to enhance detection capability, then the avalanche gain and detection efficiency are improved, but the noise from afterpulsing and delayed crosstalk increases
Solution Approach 1:
The patent extracts and removes minority carriers (holes) from the substrate using gettering regions, preventing them from causing delayed crosstalk and afterpulsing. This extraction of harmful carriers allows the device to operate at high bias voltages without the associated noise penalties
Solution Approach 2:
The gettering regions act as intermediary structures that capture and remove minority carriers before they can cause harmful effects. These regions serve as a mediator between the high-voltage operation and the noise reduction, enabling both detection efficiency and low noise performance
2Object-generated harmful factors
If the photodiode size is reduced to minimize optical crosstalk, then the delayed crosstalk is reduced, but the sensing efficiency and active area are compromised
Solution Approach 1:
Instead of reducing photodiode size to minimize crosstalk, the patent extracts minority carriers from the substrate using gettering regions. This maintains full photodiode active area while removing the source of delayed crosstalk, preserving both sensing efficiency and low crosstalk performance
3Measurement precision
If the minority carrier lifetime is extended to improve charge collection, then the detection sensitivity is enhanced, but the delayed crosstalk and afterpulsing are exacerbated
Solution Approach 1:
The patent converts the potentially harmful long-lived minority carriers into a beneficial mechanism by using gettering regions to actively manage their lifetime. The minority carriers are extracted and removed in a controlled manner, transforming them from a source of noise into a controlled process that maintains detection sensitivity while preventing delayed crosstalk
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 design achieves low noise and high sensing efficiency without reducing overvoltage or active area, enabling integration in large-area arrays with improved signal-to-noise ratio and compatibility with CMOS manufacturing processes.
Implementation Method 1
generation of a single electron-hole pair, caused by absorption in the depleted region of a photon impinging upon the SPAD
Implementation Method 2
ionization process. This ionization process in turn causes an avalanche carrier multiplication
Implementation Method 3
the photons generated by electroluminescence during processes of avalanche multiplication triggered in surrounding SPADs
Implementation Method 4
this minority carrier (for example, a hole, in the case of a substrate of an N type) can diffuse until the depleted region of i) the original SPAD or else ii) another SPAD of the array is reached
Data Source
AI summary
In at least one embodiment, a Geiger-mode avalanche photodiode, including a semiconductor body, is provided. The semiconductor body includes a semiconductive structure and a front epitaxial layer on the semiconductive structure. The front epitaxial layer has a first conductivity type. An anode region having a second conductivity type that is different from the first conductivity type extends into the front epitaxial layer. The photodiode further includes a plurality of gettering regions in the semiconductive structure.