SPAD Doping Structure for Low-Noise Stable Breakdown
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Solution Overview
Problem
Current single-photon avalanche diodes (SPADs) face challenges with noise characteristics, breakdown voltage, and operational stability, particularly due to premature breakdown phenomena and single-channel effects, which affect their efficiency and reliability in detecting single photons.
Innovation Solution
The design incorporates a heavily doped region, a lightly doped region, a guard ring, and a well structure with specific conductivity types and doping concentrations to form depletion regions and improve electric field distribution, reducing tunneling noise and trap-assisted tunneling noise, and eliminating the need for a guard ring, thereby enhancing breakdown characteristics and operational stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a guard ring is provided on the side surface of the first lightly doped region, then breakdown characteristics are improved, but device complexity increases
Solution Approach 1:
The patent removes the guard ring component from the SPAD structure while maintaining breakdown characteristics through optimized doping profiles in the lightly doped region and well structure, thereby simplifying the device architecture without sacrificing reliability
Solution Approach 2:
The patent applies non-uniform doping concentrations in different regions (heavily doped region, lightly doped region with specific concentration gradients, and well structure) to achieve optimal electric field distribution and breakdown characteristics without requiring additional guard ring structures
2Object-affected harmful factors
If heavily doped regions and well structures are optimized, then noise characteristics are improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes specific doping concentration parameters in the heavily doped region, lightly doped region, and well structure to suppress tunneling noise and trap-assisted tunneling noise, achieving improved noise characteristics through carefully controlled parameter ranges that balance performance with manufacturability
3Productivity
If the breakdown voltage is reduced, then single-photon detection efficiency is improved, but operational stability deteriorates
Solution Approach 1:
The patent creates different doping concentration zones (heavily doped region, lightly doped region with gradient, and well structure) that locally control the electric field distribution, enabling reduced breakdown voltage for high detection efficiency while maintaining operational stability through the structured doping profile
Solution Approach 2:
The patent extends the doping structure into multiple dimensions with the well structure covering the lightly doped region, creating a three-dimensional doping architecture that controls breakdown characteristics and maintains stability across different spatial dimensions
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 SPADs exhibit enhanced noise characteristics, reduced breakdown voltage, and increased operational stability, allowing for more efficient single-photon detection across a wide wavelength band without forming a guard ring, leading to improved performance and reliability.
Implementation Method 1
a heavily doped region, a first lightly doped region covering the heavily doped region, a guard ring provided on a side surface of the first lightly doped region
Implementation Method 2
to form depletion regions and improve electric field distribution
Implementation Method 3
When a photon with enough energy to release the electron reaches the photo diode, an electron-hole pair (EHP) is generated
Implementation Method 4
The high electric field accelerates the photo-generated electrons quickly to (+) side, and the additional electrons-hole pairs are generated in succession by the impact ionization by such acceleration electrons
Data Source
AI summary
Disclosed is a single-photon avalanche diode comprises a heavily doped region, a first lightly doped region covering the heavily doped region, a guard ring provided on a side surface of the first lightly doped region, a first well covering the first lightly doped region and the guard ring, and a contact electrically connected to the first well. The heavily doped region, the first lightly doped region, and the guard ring have a first conductivity type. The first well and the contact have a second conductivity type.