Silicon Waveguide PN Junction Layout for Higher Modulation Overlap
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Solution Overview
Problem
The modulation efficiency of silicon PN junction phase shifters in optoelectronic devices is limited by the overlap between the optical mode and the PN junction area.
Innovation Solution
An optoelectronic device is designed with an optical waveguide in a silicon-on-insulator wafer, featuring a semiconductor junction with a first doped region extending horizontally and vertically over a second doped region, and a third portion protruding as a salient into the second doped region, increasing the junction length within the optical mode area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional symmetrical PN junction structure is used, then the device structure is simple and easy to manufacture, but the overlap between the optical mode and the PN junction area is limited, reducing modulation efficiency
Solution Approach 1:
The patent applies asymmetry by designing an asymmetric PN junction structure where the first doped region extends beyond the second doped region to form a salient protrusion. This asymmetric configuration increases the overlap area between the optical mode and the PN junction, thereby improving modulation efficiency while maintaining manufacturability through standard doping processes.
Solution Approach 2:
The patent extends the first doped region in multiple spatial dimensions - horizontally on top of the second doped region, vertically along its lateral side, and protruding into it to form a salient. This multi-dimensional extension maximizes the junction overlap with the optical mode volume, resolving the contradiction between simple structure and high modulation efficiency.
2Productivity
If the PN junction area is increased to improve optical mode overlap, then modulation efficiency improves, but the device area and manufacturing complexity increase
Solution Approach 1:
The patent applies local quality by concentrating the doped regions precisely where the optical mode intensity is highest. The first doped region is strategically positioned to overlap with the optical mode area, creating high doping concentration zones exactly where they are most effective for modulation, rather than uniformly distributing doping throughout the device.
Solution Approach 2:
The patent employs a nested configuration where the first doped region is partially contained within the vertical projection of the second doped region, while also extending beyond it. The salient protrusion of the first doped region into the second doped region creates a nested arrangement that maximizes overlap volume without proportionally increasing the overall device footprint.
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 the overlap between the optical mode and the semiconductor junction, thereby improving the modulation efficiency of the optoelectronic device.
Implementation Method 1
Optical modulation of light in a silicon waveguide is known, including waveguide modulators based upon: electro-optic, quantum confined Stark, Franz-Keldysh, and carrier plasma dispersion
Implementation Method 2
a semiconductor junction comprising: a first doped region of semiconductor material; and a second doped region of semiconductor material, the second doped region containing dopants of a different species to the first doped region
Data Source
AI summary
An optoelectronic device comprising an optical waveguide formed in a silicon device layer of a silicon-on-insulator wafer. The optical waveguide including a semiconductor junction comprising a first doped region of semiconductor material and a second doped region of semiconductor material. The second doped region containing dopants of a different species to the first doped region. A first portion of the first doped region extends horizontally on top of the second doped region, a second portion of the first doped region extends vertically along a lateral side of the second doped region and a third portion of the first doped region protrudes as a salient from the first or second portion of the first doped region into the second doped region.