Electro-optic Device Insulating Structure for High Speed Modulation
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Solution Overview
Problem
Existing silicon-based electro-optic modulators face challenges in achieving high phase efficiency and speed due to limitations in free carrier concentration modulation, with p-i-n diodes offering high refractive index variation but slow speed, and MOS capacitors providing high speed but low effective refractive index change.
Innovation Solution
An electro-optic device with a semiconducting region doped with doping atoms of a first conductivity type and a second semiconducting region doped with doping atoms of a second conductivity type, featuring an electro-optic active region with a dielectric structure extending perpendicular to the surface, enhancing optical overlap and phase modulation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If p-i-n diodes are used for free carrier concentration modulation, then high effective refractive index variation is achieved, but modulation speed is limited to below 1 GHz due to long carrier recombination process
Solution Approach 1:
The device is segmented into distinct functional regions: a first semiconducting region with first conductivity type, a second semiconducting region with second conductivity type, and an intrinsic electro-optic active region between them. This segmentation allows independent optimization of each region's properties, enabling high refractive index variation in the intrinsic region while maintaining fast modulation speed through the doped contact regions.
Solution Approach 2:
The patent introduces an intrinsic semiconductor region as an intermediary between the doped semiconducting regions. This intrinsic region serves as the electro-optic active region where free carrier concentration can be rapidly modulated by applying voltage across the p-n junction, achieving both high refractive index variation and fast modulation speed without the limitations of traditional p-i-n diodes or MOS capacitors.
2Speed
If MOS capacitors are used for modulation, then high speed and zero DC power are achieved, but effective real refractive index change is low due to small free carrier optical overlap
Solution Approach 1:
The patent transitions from the two-dimensional planar structure of MOS capacitors to a three-dimensional vertically stacked p-n junction structure. This dimensional change allows the electro-optic active region to extend through the thickness of the intrinsic layer, increasing the optical overlap volume and enhancing the effective refractive index change while maintaining fast modulation speed.
Solution Approach 2:
The device employs a composite structure combining doped semiconducting regions (for electrical contact and field application) with an intrinsic electro-optic active region (for high refractive index modulation). This composite architecture leverages the advantages of both doped and intrinsic semiconductor materials to achieve simultaneous high speed and high effective refractive index variation.
3Quantity of substance
If a long phase shifter length is used to achieve π phase shift with MOS capacitors, then signal modulation is achieved, but device length and complexity increase
Solution Approach 1:
The patent changes the key parameter of free carrier concentration in the electro-optic active region by applying voltage across the p-n junction. This electrical parameter change directly modulates the refractive index in the intrinsic region, enabling π phase shift to be achieved in a compact length without requiring long phase shifters, thereby reducing device complexity and improving integration density.
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
The solution achieves both high phase efficiency and high speed, with a VπLπ figure-of-merit of approximately 0.36 Vcm and a modulation bandwidth exceeding 40 GHz, while minimizing DC power consumption and optical loss.
Implementation Method 1
In silicon, the modulation mechanism is dominated by free-carrier plasma dispersion effect (FCPD). The FCPD effect occurs when a variation in the free carrier concentration causes a corresponding change in refractive index and optical extinction coefficient or absorption coefficient, leading to phase-shift.
Data Source
AI summary
An electro-optic device is disclosed. The electro-optic device includes an insulating layer, a first semiconducting region disposed above the insulating layer and being doped with doping atoms of a first conductivity type, a second semiconducting region disposed above the insulating layer and being doped with doping atoms of a second conductivity type and an electro-optic active region disposed above the insulating layer and between the first semiconducting region and the second semiconducting region. The electro-optic active region includes a first partial active region and a second partial active region and an insulating structure in between. The insulating structure extends perpendicular to the surface of the insulating layer such that there is no overlap of the first partial active region and the second partial active region in the direction perpendicular to the surface of the insulating layer. A method for manufacturing is also disclosed.