Waveguide Photodetector Bridge Structure for High Speed
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Solution Overview
Problem
Waveguide photodetectors face challenges in maximizing operation speed and electrical characteristics, while also requiring complex manufacturing processes and high costs due to the need for multiple unit processes in forming the absorption layer.
Innovation Solution
The design includes a waveguide photodetector with a waveguide layer, an absorption layer, and electrodes, where bridges formed by trenches in the waveguide layer electrically connect the absorption layer to the second electrode, and a doped layer provides ohmic contact, reducing the number of manufacturing steps and improving conductivity, with a passivation layer to confine incident light and enhance optical and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple unit processes are used to form the absorption layer, then manufacturing precision can be improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the absorption layer formation into the waveguide layer fabrication process itself. By using a single-mode waveguide layer with specific refractive index and thickness to serve as the absorption layer, the device eliminates the need for separate absorption layer deposition processes, thereby reducing manufacturing complexity while maintaining precision through the waveguide's inherent optical confinement properties
Solution Approach 2:
The waveguide layer is designed to perform multiple functions simultaneously: it guides light through total internal reflection and also serves as the absorption layer for photodetection. This multi-functionality is achieved by optimizing the waveguide layer's refractive index (1.4-2.5) and thickness (0.5-5 μm) to enable both effective light confinement and sufficient light absorption for carrier generation
2Volume of moving object
If the second electrode is placed close to the absorption layer, then device size is reduced, but electrical characteristics and operation speed deteriorate
Solution Approach 1:
The patent introduces a bridge structure as an intermediary element between the absorption layer and the second electrode. This bridge, formed by removing waveguide layer material to create trenches and leaving remaining waveguide portions, provides an electrical conduction path that allows the second electrode to be positioned closer to the absorption layer without compromising electrical characteristics or operation speed
3Reliability
If the waveguide layer is removed between absorption layer and second electrode, then electrical characteristics improve, but operation speed decreases due to optical loss
Solution Approach 1:
The patent segments the waveguide layer removal process by creating multiple trenches rather than completely removing the waveguide layer. These trenches are spaced at specific intervals, allowing electrical connection while minimizing optical loss. The segmented approach enables the waveguide to maintain light guidance functionality while providing electrical access to the absorption layer
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 enhances operation speed, reduces manufacturing costs, and improves electrical characteristics by simplifying the manufacturing process and increasing productivity, with a 3-dB bandwidth of up to 47 GHz and low dark current, effectively addressing the limitations of existing waveguide photodetectors.
Implementation Method 1
incident light traveling along a waveguide having a relative higher refractive index than a substrate
Implementation Method 2
incident light is coupled to an absorption layer by an optical coupling phenomenon such as an evanescent coupling or a radiation mode
Implementation Method 3
the light absorbed in the absorption layer is detected as current through an electro-optic conversion
Implementation Method 4
a doped layer provides ohmic contact
Data Source
AI summary
Provided is a waveguide photodetector that may improve an operation speed and increase or maximize productivity. The waveguide photodetector includes a waveguide layer extending in a first direction, an absorption layer disposed on the waveguide layer, a first electrode disposed on the absorption layer, a second electrode disposed on the waveguide layer, the second electrode being spaced from the first electrode and the absorption layer in a second direction crossing the first direction, and at least one bridge electrically connecting the absorption layer to the second electrode.