Dual-Switch GeSi Photodiode for High-Speed Near-IR Sensing
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Solution Overview
Problem
Conventional photodiodes using silicon as an absorption material for near-infrared wavelengths suffer from slow photo-carrier generation and limited operation speed due to inefficient absorption, which affects depth resolution in time-of-flight applications.
Innovation Solution
The use of a dual-switch photodiode with a germanium-silicon (GeSi) absorption layer, where two groups of switches collect photo-carriers at different optical phases, allowing for enhanced operation speed and depth resolution by utilizing the efficient absorption properties of germanium for near-infrared wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If silicon is used as absorption material for near-infrared wavelengths, then the device structure is simple and manufacturing is easier, but photo-carrier generation is slow and operation speed is limited
Solution Approach 1:
The patent employs a germanium-silicon (GeSi) absorption layer that combines the efficient near-infrared absorption properties of germanium with the mechanical strength and manufacturing compatibility of silicon. This composite material structure achieves both high photo-carrier generation speed and ease of manufacture, as the GeSi layer can be integrated onto standard silicon substrates using established semiconductor fabrication processes.
Solution Approach 2:
The patent modifies the material composition parameter of the absorption layer by incorporating germanium into silicon, creating a GeSi alloy with optimized properties. By adjusting the germanium concentration in the absorption layer, the patent achieves enhanced near-infrared absorption efficiency while maintaining compatibility with existing silicon-based manufacturing processes.
2Measurement precision
If a single photodiode structure is used, then the device complexity is low, but depth resolution in time-of-flight applications is limited
Solution Approach 1:
The patent divides the photodiode structure into multiple functional regions within the absorption layer, including a first region and a second region with different doping concentrations. This segmentation allows different portions of the absorption layer to optimize for different aspects of photo-carrier generation and collection, thereby improving depth resolution while keeping the overall device structure manageable through systematic regional differentiation.
Solution Approach 2:
The patent introduces a vertical dimension to the photodiode structure by creating multiple regions at different depths within the absorption layer. The first region and second region are positioned at different vertical positions, allowing photo-carriers generated at different depths to be collected by appropriately positioned collection regions, thereby enhancing depth resolution through three-dimensional structural optimization.
3Productivity
If germanium-silicon absorption layer is used to improve photo-carrier generation speed, then operation speed increases, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes the germanium concentration parameter in the GeSi absorption layer to achieve the best balance between photo-carrier generation speed and manufacturing feasibility. By carefully controlling the germanium content and the thickness of different regions within the absorption layer, the patent maximizes operation speed while keeping the structure compatible with standard semiconductor fabrication processes.
Solution Approach 2:
The patent applies different doping concentrations and material compositions to specific regions within the absorption layer. The first region and second region have locally optimized properties tailored to their specific functions in photo-carrier generation and collection. This local quality differentiation allows each region to perform optimally without requiring the entire structure to be overly complex.
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 improves the signal-to-noise ratio and increases the modulation frequency, enabling higher depth resolution while maintaining power consumption, by leveraging the efficient absorption of germanium and reducing the transit distance of photo-carriers.
Implementation Method 1
a germanium-silicon layer coupled to the semiconductor substrate, the germanium-silicon layer including a photodiode region configured to absorb photons and to generate photo-carriers from the absorbed photons
Data Source
AI summary
An apparatus including a semiconductor substrate; an absorption layer coupled to the semiconductor substrate, the absorption layer including a photodiode region configured to absorb photons and to generate photo-carriers from the absorbed photons; one or more first switches controlled by a first control signal, the one or more first switches configured to collect at least a portion of the photo-carriers based on the first control signal; and one or more second switches controlled by a second control signal, the one or more second switches configured to collect at least a portion of the photo-carriers based on the second control signal, where the second control signal is different from the first control signal.