Avalanche Photodiode p-Type Region Layout for Excess-Light Resistance
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Solution Overview
Problem
Electron-multiplication type avalanche photodiodes (APDs) face issues with excessive photo-electric current generation and heat deterioration due to high-intensity light incidence, as the multiplication layer is positioned between the semiconductor substrate and light absorption layer, leading to uneven current multiplication and potential breakdown.
Innovation Solution
A semiconductor light-receiving element with a p-type region structured into a first p-type portion as the central portion and a second p-type portion on the outer periphery, where the second p-type portion has a higher current multiplication factor than the first, is formed within the window layer, allowing for controlled current distribution and reduced heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the multiplication layer is positioned between the semiconductor substrate and light absorption layer in an electron-multiplication type APD, then high-speed and low-noise operation is achieved, but excessive photo-electric current generation and heat deterioration occur due to uneven current multiplication
Solution Approach 1:
The patent applies local quality by creating a non-uniform doping concentration distribution within the p-type region. The doping concentration is higher at the peripheral portion and lower at the central portion, causing the electric field and current multiplication to be concentrated at the periphery rather than uniformly distributed. This local variation in doping quality resolves the contradiction by directing the high-speed electron multiplication away from the heat-prone central region to the cooler peripheral regions.
Solution Approach 2:
The patent segments the p-type region into functionally distinct zones: a central portion with lower doping concentration and an peripheral portion with higher doping concentration. This segmentation allows different regions to perform different functions - the central region handles light absorption while the peripheral region handles electron multiplication, thereby separating the heat-generating multiplication process from the light-receiving function and reducing overall heat deterioration.
2Power
If high-intensity light is incident on the p-type region, then photo-electric current increases, but heat generation causes characteristic deterioration and potential breakdown
Solution Approach 1:
By implementing non-uniform doping concentration with higher concentration at the periphery and lower concentration at the center, the patent creates localized regions with different thermal and electrical characteristics. The peripheral high-doping region acts as a heat sink and current distributor, preventing excessive heat accumulation in the central light-receiving region while maintaining high photo-electric current generation capability.
Solution Approach 2:
The p-type region with non-uniform doping acts as an intermediary structure between the light absorption layer and the multiplication layer. It mediates the energy conversion process by first generating photo-electric current from incident light and then distributing this current through the non-uniform doping structure to peripheral regions, thereby decoupling the light-receiving function from the heat-generating multiplication function.
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 structure effectively suppresses the deterioration of characteristics by distributing excessive current through the second p-type portion, reducing heat-related issues and maintaining high sensitivity and resistance to excessive light, thereby extending the APD's lifespan.
Implementation Method 1
when the electric field intensity in its multiplication layer is increased by voltage application, avalanche multiplication occurs and thus, it is possible to amplify carriers
Implementation Method 2
carriers generated in its light absorption layer due to incident light
Data Source
AI summary
A semiconductor light-receiving element (50) is a semiconductor light-receiving element in which a multi-plication layer (2), an electric-field control layer (3), a light absorption layer (4) and a window layer (5) are sequentially formed on a semiconductor substrate (1), and a p-type region (6) is formed in the window layer (5). The p-type region (6) has a first p-type portion (14) and a second p-type portion (15) whose current multiplication factor due to light incidence is larger than that of the first p-type portion (14). The first p-type portion (14) is formed as a central portion of the p-type region (6), the central portion including a central axis (21c) perpendicular to the semiconductor substrate (1), and the second p-type portion (15) is formed on an outer periphery of the central portion in a radial direction about the central axis (21c).