Reflective Grating Photodetector for High-Bandwidth Light Absorption
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Solution Overview
Problem
High-speed optical communication photodetectors face challenges in reducing RC delay and increasing bandwidth while maintaining optical responsivity, as thinner absorption layers lead to insufficient optical absorption efficiency and higher manufacturing costs with existing reflective mirror structures.
Innovation Solution
A photodetector with an integrated reflective grating structure, featuring a substrate, active layer, and a grating structure between them, with doped regions of different types forming a PIN junction, achieving nearly total reflection and broader absorption spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thickness of the optical absorption layer is reduced to increase bandwidth and reduce transit time, then the detection speed is improved, but the optical absorption efficiency decreases and responsivity suffers
Solution Approach 1:
The patent combines the optical absorption layer with a grating structure to form an integrated device. The grating is formed directly within the absorption layer through selective doping, merging the light-trapping function with the absorption function. This integration allows the thin absorption layer to maintain high optical absorption efficiency through enhanced light confinement while keeping the thickness reduced for fast carrier transit.
Solution Approach 2:
The grating structure acts as an intermediary that enhances the interaction between incident light and the thin absorption layer. By creating periodic modulation in the absorption layer, the grating mediates the coupling of light into guided modes, increasing the effective optical path length and absorption efficiency without requiring a thicker absorption layer.
2Reliability
If conventional reflective mirror structures (DBR or metal mirror) are used to improve optical absorption rate, then the light absorption efficiency is enhanced, but the manufacturing cost and process complexity increase significantly
Solution Approach 1:
The patent merges the grating structure formation with the absorption layer fabrication process. The grating is created by selective doping within the absorption layer itself, eliminating the need for separate DBR or metal mirror structures. This integration reduces the number of manufacturing steps while achieving comparable or superior optical absorption performance.
Solution Approach 2:
The absorption layer serves its dual function: it absorbs incident light and simultaneously provides the medium in which the grating structure is formed through selective doping. The absorption layer essentially creates its own light-trapping structure, eliminating the need for external reflective mirrors and simplifying the overall device architecture.
3Reliability
If conventional reflective mirror structures are used to enhance optical absorption, then the absorption rate improves, but the manufacturing cost increases due to additional process steps
Solution Approach 1:
The patent combines multiple functions into a single integrated structure. The grating-formed absorption layer simultaneously provides optical absorption, light trapping, and carrier generation functions that would otherwise require separate components. This reduces material costs and manufacturing complexity while maintaining high optical absorption rates.
Solution Approach 2:
The patent extracts the light-trapping function from separate reflective mirror components and integrates it directly into the absorption layer through grating formation. This eliminates the need for additional expensive materials (such as metal mirrors or complex DBR structures) and reduces overall manufacturing cost.
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 design enhances bandwidth and optical responsivity, allowing for increased detection speed and light absorption efficiency while reducing manufacturing costs and complexity.
Implementation Method 1
a grating structure disposed between the substrate and the active layer... achieving nearly total reflection and broader absorption spectra
Implementation Method 2
enhances bandwidth and optical responsivity, allowing for increased detection speed and light absorption efficiency
Implementation Method 3
A first doped region is formed on the substrate at a location near the grating structure. A second doped region is formed on a surface of the active layer away from the grating structure. The doping type of the second doped region is different from that of the first doped region.
Data Source
AI summary
A photodetector with an integrated reflective grating structure includes a substrate, an active layer disposed on the substrate, and a grating structure disposed between the substrate and the active layer. A first doped region is formed on the substrate at a location near the grating structure. A second doped region is formed on a surface of the active layer away from the grating structure. The doping type of the second doped region is different from that of the first doped region.