Silicon Photodiode Array With Irregular Asperity
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Solution Overview
Problem
Conventional silicon photodiodes have limited spectral sensitivity in the near-infrared wavelength band and are expensive to manufacture, with complex processes involved in their production.
Innovation Solution
A silicon photodiode array is developed with an epitaxial semiconductor layer forming pn junctions and multiplication regions on a silicon substrate, featuring an irregular asperity on the surface to enhance light absorption and reduce dark current, eliminating the need for guard rings and allowing for higher aperture rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional silicon photodiodes are used, then manufacturing cost is low and manufacturing process is simple, but spectral sensitivity in the near-infrared wavelength band is insufficient
Solution Approach 1:
The photodiode structure is segmented into distinct functional layers: a silicon substrate with an n-type semiconductor layer, a p-type semiconductor layer forming pn junctions, and a multiplication region. This segmentation allows each layer to be optimized for its specific function while maintaining compatibility with standard silicon manufacturing processes, thereby improving near-infrared spectral sensitivity without significantly increasing manufacturing complexity
Solution Approach 2:
The invention changes key material parameters by introducing a p-type semiconductor layer with specific doping concentrations and forming a multiplication region with controlled electric fields. These parameter changes enable the silicon photodiode to detect near-infrared wavelengths beyond the conventional 1100 nm limit, enhancing spectral sensitivity while using standard silicon-based fabrication techniques
2Reliability
If compound semiconductor photodiodes are used, then spectral sensitivity in the near-infrared wavelength band is improved, but manufacturing cost increases and manufacturing process becomes complicated
Solution Approach 1:
The invention replaces expensive compound semiconductor materials with standard silicon, which is abundant and inexpensive. The silicon-based photodiode achieves near-infrared detection capability through structural design (pn junctions and multiplication regions) rather than relying on expensive material composition, thereby reducing both material cost and manufacturing complexity while maintaining adequate spectral sensitivity
Solution Approach 2:
Instead of changing material composition to achieve near-infrared sensitivity, the invention changes structural parameters: introducing a p-type layer to form pn junctions and creating a multiplication region with high electric fields. These parameter changes enable silicon to detect near-infrared wavelengths without requiring complex compound semiconductor fabrication processes
3Reliability
If guard rings are added to prevent edge breakdown, then reliability is improved, but aperture rate decreases
Solution Approach 1:
Instead of adding guard rings around the active area to prevent edge breakdown (which reduces aperture rate), the invention inverts the approach by optimizing the pn junction formation and multiplication region structure to inherently prevent edge effects. The p-type semiconductor layer is configured to extend to the edges, creating a field-stop effect that prevents edge breakdown without requiring additional guard ring structures, thereby maintaining high aperture rate while ensuring reliability
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 solution provides improved spectral sensitivity in the near-infrared wavelength band, reduces dark current, and simplifies the manufacturing process, making the silicon photodiode array more cost-effective and efficient.
Implementation Method 1
an irregular asperity is formed in at least a surface corresponding to the photodetecting channels in the semiconductor layer of the first conductivity type
Implementation Method 2
carriers generated with incidence of the detection target light
Implementation Method 3
a plurality of multiplication regions for avalanche multiplication of carriers generated with incidence of the detection target light
Data Source
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AI summary
A photodiode array PDA1 is provided with a substrate S wherein a plurality of photodetecting channels CH have an n-type semiconductor layer 32. The photodiode array PDA1 is provided with a p type semiconductor layer 33 formed on the n-type semiconductor layer 32, resistors 24 provided for the respective photodetecting channels CH and each having one end portion connected to a signal conducting wire 23, and an n-type separating portion 40 formed between the plurality of photodetecting channels CH. The p type semiconductor layer 33 forms pn junctions at an interface to the n-type semiconductor layer 32 and has a plurality of multiplication regions AM for avalanche multiplication of carriers generated with incidence of detection target light, corresponding to the respective photodetecting channels. An irregular asperity 10 is formed in a surface of the n-type semiconductor layer 32 and the surface is optically exposed.