Graphene Electrode Modulator via CVD Growth
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Solution Overview
Problem
Existing electro-optic modulators using graphene face challenges in achieving reliable and scalable production due to contamination, physical damage, and reduced quality during mechanical transfer processes, which affect the device's performance and consistency.
Innovation Solution
The development of an electro-optic modulator with a graphene layer as a first electrode and a non-graphene layer as a second electrode, where the graphene is grown directly by Chemical Vapor Deposition (CVD) on a silicon nitride waveguide, reducing contact resistance and impurities, and using a non-graphene second electrode to enhance modulation speed and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mechanical transfer process is used to place graphene on waveguide, then device fabrication is enabled, but contamination and physical damage occur reducing graphene quality
Solution Approach 1:
The patent applies preliminary action by pre-growing graphene on a copper substrate using CVD before transferring to the waveguide. This preliminary growth step enables controlled, high-quality graphene formation with uniform structure and desired electrical properties, which is then transferred to the final device position. The preliminary action on copper substrate ensures graphene quality before the mechanical transfer process.
Solution Approach 2:
The patent uses a copper substrate as an intermediary material for graphene growth. The copper substrate serves as a mediator that facilitates controlled CVD growth of high-quality graphene, which is then transferred to the waveguide. This intermediary approach separates the growth process from the final device structure, allowing optimization of graphene quality during growth on copper while enabling subsequent integration onto the waveguide.
2Speed
If graphene is used as electrode material, then carrier mobility and modulation speed are improved, but contact resistance and energy consumption increase
Solution Approach 1:
The patent employs composite materials by combining graphene with metal contact materials (such as titanium, nickel, or copper) to create hybrid electrode structures. The graphene layer provides high carrier mobility and fast modulation speed, while the metal contacts provide low contact resistance. This composite approach synergistically combines the advantages of both materials to achieve both high speed and low energy consumption.
Solution Approach 2:
The patent applies parameter changes by optimizing the work function of contact materials and adjusting doping levels in graphene to minimize contact resistance. By changing material parameters such as contact material selection, contact geometry, and graphene doping concentration, the device achieves low contact resistance while maintaining high modulation speed, thereby reducing energy consumption.
3Ease of manufacture
If mechanical transfer process is used, then graphene can be placed on waveguide, but production scalability and consistency are reduced
Solution Approach 1:
The patent uses preliminary action by growing graphene on large-area copper substrates before waveguide fabrication. This allows parallel processing of multiple devices and enables wafer-scale production. The preliminary CVD growth step can be performed on entire wafers simultaneously, and subsequent transfer processes can batch-process multiple devices, significantly improving production scalability and consistency.
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 approach results in improved carrier mobility, reduced energy consumption, and increased modulation speed, while avoiding the drawbacks of mechanical transfer, enabling the production of high-quality graphene-based modulators suitable for commercial photonic devices with enhanced reliability and consistency.
Implementation Method 1
The principle of operation is based on the electro-optic effect which is the modification of the refractive index of a medium, caused by an electric field. Graphene has been used in electro-optic devices such as electro-optic modulators... the modulation is achieved by actively tuning the Fermi level of a monolayer graphene sheet and therefore its transparency.
Implementation Method 2
The development of an electro-optic modulator with a graphene layer as a first electrode... where the graphene is grown directly by Chemical Vapor Deposition (CVD) on a silicon nitride waveguide
Data Source
AI summary
There is provided an electro-optic modulator comprising: a substrate having a first channel of waveguide material embedded therein, the substrate and the waveguide material together providing a substantially flat upper surface, a first insulative layer on and across the upper surface; a graphene layer arranged on the first insulative layer and over at least a first portion of the first channel of waveguide material; and a second insulative layer provided on and across the graphene layer; wherein the graphene layer provides a first electrode, and wherein a, preferably non-graphene, second electrode is either: (i) provided on the second insulative layer at least overlapping the first portion of the first channel of waveguide material, or (ii) provided within the substrate at least underlapping the first portion of the first channel of waveguide material.