SiGe Waveguide Modulator Without Buried Oxide
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Solution Overview
Problem
Conventional optoelectronic devices operating at 1310 nm wavelengths face issues such as large footprint, high parasitic capacitance, polarization dependency, and limited operational bandwidth due to the necessity of a silicon seed layer and buried oxide layer, which complicates manufacturing and affects performance.
Innovation Solution
An optoelectronic device is designed without a buried oxide layer, using an epitaxial crystalline cladding layer with a lower refractive index than the optically active region, which is regrown to replace the traditional buried oxide layer, optimizing mode match and reducing device losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buried oxide layer and silicon seed layer are used in conventional optoelectronic devices, then the device structure is stable and light confinement is achieved, but the device footprint becomes large, parasitic capacitance increases, and manufacturing complexity increases
Solution Approach 1:
The patent removes the buried oxide layer from the conventional waveguide structure, extracting the problematic insulating layer that caused large footprint and high parasitic capacitance. The silicon seed layer is also eliminated by directly growing the active region on the silicon substrate, simplifying the manufacturing process while maintaining device stability through alternative light confinement mechanisms.
Solution Approach 2:
The patent changes the refractive index profile by removing the buried oxide layer (which had high refractive index) and replacing it with air or low-index materials at the substrate interface. This parameter change enables direct growth of active regions on silicon substrates while maintaining effective light confinement through modified mode matching conditions.
2Reliability
If a buried oxide layer is used for light confinement, then optical modes are confined effectively, but coupling loss between waveguides increases and device speed decreases due to RF parasitic capacitance
Solution Approach 1:
The buried oxide layer is removed to eliminate the high-parasitic-capacitance interface that caused signal loss and slowed device response. Light confinement is maintained through direct optical contact between the active region and the silicon substrate, which provides effective mode matching without the intermediate oxide layer.
Solution Approach 2:
The silicon substrate itself acts as the new intermediary between the active region and the underlying structure, providing both mechanical support and optical confinement through its high refractive index, replacing the function previously performed by the buried oxide layer.
3Manufacturing precision
If a silicon seed layer is deposited to enable epitaxial growth of the active region, then crystal structure quality is improved, but the manufacturing process becomes more complex and yield decreases
Solution Approach 1:
The separate silicon seed layer deposition step is removed from the manufacturing process. The active region is grown directly on the silicon substrate using epitaxial techniques, eliminating the intermediate seed layer formation step while maintaining crystal structure quality through direct substrate-to-active-region growth.
Solution Approach 2:
The functions of the silicon substrate (mechanical support) and silicon seed layer (crystal template) are merged into a single step where the silicon substrate directly serves as both support and growth template for the active region, simplifying the overall manufacturing process.
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 reduces coupling loss, minimizes RF parasitic capacitance, and enhances device speed, making the optoelectronic device less polarization dependent and less sensitive to manufacturing process variations.
Implementation Method 1
the epitaxial crystalline cladding layer has a refractive index which is less than a refractive index of the optically active region, such that optical power is confined to the optically active region
Data Source
AI summary
An optoelectronic device and method of making the same. In some embodiments, the optoelectronic device includes a substrate, a Mach-Zehnder waveguide modulator, and an epitaxial crystalline cladding layer. The Mach-Zehnder waveguide modulator includes a left arm including a left SiGe optical waveguide, and a right arm including a right SiGe optical waveguide, each of the left and right optical waveguides including a junction region and a plurality of electrodes for providing a bias across the junction to enable control of the phase of light travelling through the junction regions via dispersion. The epitaxial crystalline cladding layer is on top of the substrate and beneath the junction region of the left optical waveguide and/or the junction region of the right optical waveguide, and has a refractive index which is less than a refractive index of the respective junction region(s), such that optical power is confined to the respective junction region(s).