Photodiode Array Epitaxial Junctions Edge Breakdown
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Solution Overview
Problem
Photodiode arrays with reach-through structures face limitations in increasing the ratio of opening area for light detection due to edge breakdown issues and crosstalk from avalanche multiplication, which restricts detection sensitivity and efficiency.
Innovation Solution
The photodiode array design features an epitaxial semiconductor layer forming pn junctions, eliminating edge breakdown and the need for guard rings, and incorporates a separating part between channels to reduce crosstalk, with a light shielding material to absorb or reflect unwanted light, enhancing the opening area ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guard rings are added to prevent edge breakdown, then reliability is improved, but the opening area ratio deteriorates
Solution Approach 1:
The invention extracts and removes the guard ring structure from the photodiode array. By forming the pn junction directly at the surface without guard rings, the patent eliminates the components that were reducing the opening area while maintaining reliability through the epitaxial layer structure that prevents edge breakdown inherently.
Solution Approach 2:
The patent transitions from a planar guard ring structure to a vertical epitaxial layer structure. By moving the junction formation into the depth dimension through epitaxial growth, the solution maintains edge protection functionality while maximizing the surface opening area for light detection.
2Productivity
If opening area is increased to improve detection efficiency, then productivity is improved, but edge breakdown risk worsens
Solution Approach 1:
The epitaxial semiconductor layer is formed in advance during the manufacturing process, creating a structured junction that inherently prevents edge breakdown before the device operates. This preliminary structural preparation allows maximum opening area to be used without risking edge breakdown during operation.
3Measurement precision
If multiplication regions are made sensitive to faint light, then measurement precision is improved, but crosstalk worsens
Solution Approach 1:
The photodiode array is segmented into multiple independent photodetector channels, each with its own multiplication region formed in the epitaxial layer. This segmentation isolates the avalanche multiplication processes, allowing each channel to detect faint light independently while preventing crosstalk between adjacent channels.
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 significantly increases the opening area ratio, improving detection efficiency and reducing crosstalk, thereby enhancing the sensitivity and performance of the photodiode array in photon counting applications.
Implementation Method 1
Each multiplication region is applied with a reverse voltage that exceeds a breakdown voltage, and then the phenomenon is used in which carriers generated by the incident photons are multiplied in an avalanche process
Implementation Method 2
carriers generated by the incident photons are multiplied in an avalanche process
Implementation Method 3
a light shielding material to absorb or reflect unwanted light
Implementation Method 4
a light shielding material to absorb or reflect unwanted light
Data Source
Figure 1
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Figure 3
AI summary
A photodiode array 1 has a plurality of photodetector channels 10 which are formed on an n-type substrate 2 having an n-type semiconductor layer 12, with a light to be detected being incident to the plurality of photodetector channels 10. The photodiode array 1 comprises: a p-type semiconductor layer 13 formed on the n-type semiconductor layer 12 of the substrate 2; resistors 4 each of which is provided to each of the photodetector channels 10 and is connected to a signal conductor 3 at one end thereof; and an n-type separating part 20 formed between the plurality of photodetector channels 10. The p--type semiconductor layer 13 forms a pn junction at the interface between the substrate 2, and comprises a plurality of multiplication regions AM for avalanche multiplication of carriers produced by the incidence of the light to be detected so that each of the multiplication regions corresponds to each of the photodetector channels. The separating part 20 is formed so that each of the multiplication regions AM of the p--type semiconductor layer 13 corresponds to each of the photodetector channels 10.