Avalanche Diode Structure for Low-Noise Charge Collection
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Solution Overview
Problem
Conventional single photon avalanche diodes (SPADs) suffer from noise due to strong local electric fields, which reduces signal accuracy in light detection devices.
Innovation Solution
A light detection device with a semiconductor substrate structure that includes a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type, and a third semiconductor region of the second conductivity type, where the second and third regions extend from a first separation region to a second separation region, allowing for efficient charge collection and reduced noise through controlled electric field distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional SPAD structure with low impurity concentration region is used, then charge collection efficiency is improved, but noise increases due to strong local electric fields
Solution Approach 1:
The patent applies local quality by creating distinct regions with different impurity concentrations and electric field characteristics. The first semiconductor region has high impurity concentration for strong charge collection, while the second semiconductor region has low impurity concentration for avalanche multiplication. The third semiconductor region provides intermediate properties. This spatial variation in material properties optimizes both charge collection efficiency and noise reduction in different locations within the device.
Solution Approach 2:
The patent segments the semiconductor structure into three distinct regions along the depth direction, each with specific impurity concentrations and functions. The first region (high impurity) handles charge collection, the second region (low impurity) performs avalanche multiplication, and the third region (intermediate impurity) provides transition and additional charge collection. This segmentation allows each region to be optimized for its specific function, resolving the contradiction between charge collection efficiency and noise.
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 proposed structure enhances signal accuracy by minimizing noise and facilitating effective charge collection, improving the sensitivity and reliability of light detection devices.
Implementation Method 1
a light detection device capable of detecting weak light of a single photon level using avalanche (electron avalanche) multiplication
Implementation Method 2
generates avalanche multiplication by photocharge caused by a single photon
Data Source
AI summary
There are provided a light detection device and a photoelectric conversion system including the light detection device including an avalanche diode including a first semiconductor region of a first conductivity type disposed at a first depth, a second semiconductor region of a second conductivity type disposed at a second depth deeper than the first depth with respect to the first surface, a third semiconductor region that is disposed at a third depth deeper than the second depth with respect to the first surface and is in contact with the second semiconductor region, and first and second separation regions each extending from the first depth to the third depth. The second semiconductor region and the third semiconductor region each extend from the first separation region to the second separation region. The first semiconductor region, the second semiconductor region, and the third semiconductor region have portions overlapping one another in planar view.