Avalanche Photodetector Layout for High Sensitivity and Miniaturization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current photodetectors face challenges in achieving high sensitivity and miniaturization while maintaining low avalanche breakdown voltage and reducing temporal and spatial fluctuations in photodetection efficiency, particularly due to limitations in avalanche multiplication region size and electric field management.
Innovation Solution
A photodetector configuration with a semiconductor substrate having a first and second conductivity type semiconductor layers, a multiplication region for avalanche multiplication, an isolation transistor, and an isolation region that separates the semiconductor layers, allowing for increased avalanche multiplication region size and reduced isolation region size, enabling higher sensitivity and miniaturization without increasing avalanche breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the multiplication region size is increased to enhance photosensitivity, then the avalanche breakdown voltage increases, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The semiconductor substrate is divided into multiple doped regions including a first doped region, second doped region, third doped region, and fourth doped region with alternating conductivity types. This segmentation creates multiple multiplication regions that can be independently optimized, allowing increased overall photosensitivity while maintaining controlled breakdown voltage through localized field management.
Solution Approach 2:
Different doped regions are assigned different conductivity types and doping concentrations to create localized electric field characteristics. The first and third doped regions have one conductivity type while the second and fourth have the opposite type, creating non-uniform local properties that optimize avalanche multiplication in specific areas without uniformly increasing the entire device's breakdown voltage.
2Volume of moving object
If the isolation region size is reduced to achieve miniaturization, then the photodetection efficiency fluctuates spatially and temporally, but the device size is reduced
Solution Approach 1:
Isolation regions are positioned between adjacent pixel regions to act as intermediary zones that electrically isolate neighboring photodetection elements. These isolation regions prevent charge carrier leakage and electrical interference between pixels, maintaining stable photodetection efficiency even as the overall device is miniaturized and pixel density increases.
Solution Approach 2:
The isolation regions are designed to create equipotential zones that stabilize the electric field distribution across the device. By maintaining consistent potential levels in isolation areas, the patent reduces spatial and temporal fluctuations in photodetection efficiency while enabling closer pixel spacing for miniaturization.
3Measurement precision
If the avalanche multiplication region is enlarged to detect low intensity light, then the avalanche breakdown voltage increases, but the energy consumption increases
Solution Approach 1:
The avalanche multiplication function is segmented across multiple doped regions rather than concentrated in a single large region. This allows the device to achieve high gain for low intensity light detection through cumulative multiplication effects in smaller, distributed regions, reducing the overall breakdown voltage and associated energy consumption compared to a single large multiplication region.
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 configuration enhances photosensitivity, reduces temporal and spatial fluctuations, and achieves miniaturization by effectively managing the electric field and avalanche breakdown voltage, leading to improved photodetection efficiency and aperture ratio.
Implementation Method 1
a charge generated in the semiconductor substrate through photoelectric conversion
Implementation Method 2
a multiplication region that is included in the first semiconductor layer and the second semiconductor layer and causes avalanche multiplication to a charge generated in the semiconductor substrate through photoelectric conversion
Data Source
AI summary
A photodetector includes: a semiconductor substrate having a first main surface and a second main surface; a first semiconductor layer that is of a first conductivity type, and is included in the semiconductor substrate and closer to the first main surface than to the second main surface; a second semiconductor layer that is of a second conductivity type different from the first conductivity type, and is included in the semiconductor substrate and interposed between the first semiconductor layer and the second main surface; a multiplication region that causes avalanche multiplication to a charge generated in the semiconductor substrate through photoelectric conversion; a circuit region disposed alongside the first semiconductor layer in a direction parallel to the first main surface; at least one isolation transistor disposed in the circuit region; and an isolation region interposed between the first semiconductor layer and the circuit region.