Photodetection Element Layout Without Guard Rings for Higher Fill Factor
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Solution Overview
Problem
Existing photodetection elements face challenges in achieving high light detection efficiency, wide light detection wavelength range, improved fill factor, and enhanced efficiency due to limitations in the design of avalanche multiplication regions and the use of guard rings.
Innovation Solution
The proposed photodetection element features a substrate with a first and second node region of opposing conductivity types, an avalanche multiplication region between them, and a buried well, which allows for improved electrical connections and a larger depletion region, enhancing photodetection efficiency and wavelength range without the need for guard rings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If guard rings are used in conventional photodetection elements, then device structure is simplified, but photodetection efficiency and fill factor are reduced
Solution Approach 1:
The patent removes the guard ring structure from the photodetection element design. By extracting this component, the patent eliminates the trade-off between structural simplicity and detection efficiency, allowing the active detection area to be maximized without the efficiency-reducing effects of guard rings.
Solution Approach 2:
The patent transitions from a conventional planar configuration to a three-dimensional stacked architecture with multiple absorption layers positioned at different depths. This dimensional change allows simultaneous achievement of high fill factor and efficient charge collection without requiring guard rings.
2Device complexity
If conventional avalanche multiplication region design is used, then device structure is simple, but light detection wavelength range is limited
Solution Approach 1:
The patent divides the light detection function into multiple segments by implementing several absorption layers with different materials and band gaps. Each layer targets specific wavelength ranges, and their combined response achieves broad spectral coverage without complicating the avalanche multiplication region design.
Solution Approach 2:
The patent employs composite material structures in the absorption layers, combining different semiconductor materials with varying band gap energies. This allows the detector to respond to a wide range of wavelengths while maintaining a relatively simple avalanche multiplication region configuration.
3Productivity
If fill factor is increased to improve detection efficiency, then more incident photons are detected, but device area occupied by non-active regions increases
Solution Approach 1:
The patent resolves the fill factor dilemma by moving charge collection nodes to different vertical positions within the substrate. This three-dimensional arrangement allows near-100% of the surface area to be active for photon detection while maintaining efficient charge collection, as the collection nodes are positioned at optimal depths rather than occupying lateral space.
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 results in improved photodetection efficiency, a wider wavelength range for light detection, and a higher fill factor, leading to more compact and efficient photodetection devices.
Implementation Method 1
A high electric field accelerates photo-generated electrons quickly toward an anode, and the additional electron-hole pairs are generated in succession by impact ionization by such accelerated electrons, and then those of the electrons accelerate toward the anode. Similarly, the high electric field accelerates photo-generated holes quickly towards a cathode, and then causes the same phenomenon. This process repeats the process leading to the avalanche multiplication of the photo-generated electrons and holes.
Implementation Method 2
the additional electron-hole pairs are generated in succession by impact ionization by such accelerated electrons
Implementation Method 3
When an incident photon with energy higher than the band gap in a semiconductor reaches a photodiode, electron-hole pairs (EHPs) are generated.
Data Source
AI summary
A photodetection element comprises a substrate having a first surface and a second surface opposite to each other, a first node region within the substrate and having a first conductivity type, a second node region within the substrate spaced apart from the first node region and having a second conductivity type different from the first conductivity type, and an avalanche multiplication region formed between the first node region and the second node region. The first node region, the avalanche multiplication region, and the second node region are arranged along a first direction parallel to the first surface.