SPAD Semiconductor Structure for Low-Noise Single-Photon Detection
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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 impurity concentration and potential gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
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 semiconductor substrate is divided into multiple distinct regions with different impurity concentrations: a first region with first impurity concentration, a second region with second impurity concentration lower than the first, and a third region with third impurity concentration lower than the second. This segmentation allows each region to perform its specific function - the first region for charge generation, the second for charge collection, and the third for avalanche multiplication - thereby reducing noise while maintaining efficient charge collection
Solution Approach 2:
Different regions of the semiconductor substrate are assigned different impurity concentrations tailored to their specific functions. The first region has higher impurity concentration for efficient charge generation, the second region has intermediate concentration for charge collection, and the third region has lowest concentration for low-noise avalanche multiplication. This local optimization of material properties resolves the contradiction between charge collection efficiency and noise reduction
2Reliability
If avalanche multiplication is enhanced for single photon detection, then detection sensitivity is improved, but noise from strong local electric fields increases
Solution Approach 1:
The avalanche multiplication function is separated into a dedicated third region with low impurity concentration, distinct from the charge collection second region. This spatial separation allows avalanche multiplication to occur in a controlled low-noise environment while charge collection occurs in the intermediate concentration region, maintaining detection sensitivity without the harmful noise effects
Solution Approach 2:
The third region is specifically designed with the lowest impurity concentration to create optimal conditions for avalanche multiplication with minimal noise generation. This local optimization of electrical properties enables high-gain single photon detection while suppressing noise from strong electric fields through the carefully controlled impurity distribution
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 avalanche multiplication, 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
the charge generated in a third semiconductor region below the second semiconductor region is easily collected in the first semiconductor region
Implementation Method 3
a light detection device capable of detecting weak light of a single photon level using avalanche (electron avalanche) multiplication
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.