Germanium Photodetector With Silicon Nitride Waveguide for Visible Light
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Solution Overview
Problem
Existing integrated germanium photodetectors using silicon waveguides face limitations due to high absorption at visible light ranges, high propagation loss, and low power handling capabilities, which restrict their applications, especially for high-power optical signals and visible light detection.
Innovation Solution
The integration of a silicon nitride launch waveguide with an optical reflector, which evanescently couples optical signals into the germanium photodetector, reducing the detector length, lowering propagation loss, and enabling efficient visible light detection and high-speed optical-to-electrical conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon waveguide is used to launch optical light into the germanium photodetector, then the optical light can be effectively launched into the Ge PD, but the silicon waveguide shows strong absorption capabilities at visible light range and high propagation loss, limiting the applications
Solution Approach 1:
The patent introduces a silicon nitride waveguide as an intermediary component between the optical source and the germanium photodetector. This mediator waveguide has low loss characteristics and does not absorb visible light, thereby enabling efficient light delivery without the propagation loss problems of silicon waveguides
Solution Approach 2:
The patent employs a composite waveguide structure combining silicon nitride and silicon materials, where the silicon nitride portion serves as the low-loss launch waveguide and the silicon portion interfaces with the germanium photodetector, leveraging the advantages of both materials
2Ease of manufacture
If a silicon waveguide is used for optical signal transmission, then the structure is simple and CMOS-compatible, but the power handling capability is low and visible light detection is limited
Solution Approach 1:
The patent applies local quality by making different portions of the waveguide system serve different functions: the silicon nitride waveguide handles visible light transmission with low loss, while the silicon waveguide portion provides CMOS compatibility and interfaces with the germanium photodetector for detection
3Reliability
If the germanium photodetector length is increased to improve absorption, then the light absorption efficiency increases, but the dark current increases and RF bandwidth decreases
Solution Approach 1:
The silicon nitride waveguide acts as an intermediary that enhances light coupling into the germanium photodetector through evanescent field interaction, allowing sufficient absorption in a shorter detector length and thereby reducing dark current while maintaining absorption efficiency
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 solution allows for effective absorption and conversion of optical signals, reduces dark current and manufacturing costs, and enhances RF bandwidth, making it suitable for high-speed and visible light applications with improved power handling and reduced propagation loss.
Implementation Method 1
evanescently coupling optical light into the integrated germanium photodetector
Implementation Method 2
the optical signal being coupled into the integrated germanium photodetector at the coupling region, such that to be absorbed by the germanium layer
Implementation Method 3
the silicon nitride launch waveguide comprising an optical reflector
Data Source
AI summary
An optical apparatus comprising an integrated germanium photodetector associated with a silicon nitride launch waveguide, the integrated germanium photodetector comprising a silicon layer, a germanium layer disposed atop the silicon layer, a plurality of conductive vias, at least one conductive via of the plurality of conductive vias being disposed atop the germanium layer, and a plurality of metal contacts each interconnected to each of the plurality of conductive vias; wherein the silicon nitride launch waveguide extends over a length of the silicon layer, and such that to create a coupling region between the silicon nitride launch waveguide and the germanium layer; and wherein, when an optical signal is launched into the silicon nitride launch waveguide, the optical signal is caused to be coupled into the integrated germanium photodetector at the coupling region, such that to be absorbed by the germanium layer.