Light Receiving Device Mesa Fabrication Isolation
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Solution Overview
Problem
Existing waveguide-type light receiving devices face challenges in achieving high electric isolation and low crosstalk between photodiode and waveguide mesa structures, which are essential for efficient signal extraction and conversion in coherent optical receivers.
Innovation Solution
A method for fabricating a light receiving device involves forming a waveguide mesa structure with a narrower width than the photodiode mesa structure, using etching masks to create side faces that provide high isolation resistance and low crosstalk, by depositing Si-based compound materials on the mesa structures during etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If waveguide mesa structure and photodiode mesa structure are integrated on the same substrate, then device functionality is improved, but electric isolation between sections deteriorates
Solution Approach 1:
The device is divided into distinct mesa structures (waveguide mesa and photodiode mesa) that are physically separated and isolated from each other. Each mesa structure is formed as an independent entity with its own lateral boundaries, preventing electrical interference while maintaining functional integration on the same substrate.
Solution Approach 2:
Different regions of the substrate are assigned different functional qualities - the waveguide mesa region is optimized for optical guidance while the photodiode mesa region is optimized for light detection. The isolation regions between mesas provide localized electrical insulation without affecting the overall device functionality.
2Ease of manufacture
If mesa structures are formed with standard etching processes, then manufacturing simplicity is maintained, but isolation resistance between structures is insufficient
Solution Approach 1:
The isolation problem is solved by extending the mesa structures vertically to form tall, narrow structures with large aspect ratios. By increasing the height dimension, the lateral isolation requirements are reduced, as the electric field confinement improves with height, achieving better isolation without complicating the horizontal fabrication process.
Solution Approach 2:
The etching process parameters are optimized to create mesa structures with specific dimensional characteristics - particularly height and top surface area ratios. By controlling these parameters, the electric field distribution is optimized to enhance isolation between adjacent mesas while maintaining manufacturability through standard etching processes.
3Device complexity
If photodiode mesa and waveguide mesa are formed with similar dimensions, then fabrication complexity is reduced, but crosstalk between sections increases
Solution Approach 1:
The photodiode mesa and waveguide mesa are designed with asymmetric dimensional relationships - specifically, the photodiode mesa has a larger top surface area relative to its height compared to the waveguide mesa. This asymmetric geometry creates different electric field confinement characteristics that reduce crosstalk while the fabrication process remains relatively simple by using the same basic etching steps for both structures.
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 approach enhances electric isolation between light receiving sections and reduces crosstalk, improving the efficiency of signal extraction and conversion in coherent optical receivers.
Implementation Method 1
etching the first substrate product with the first mask and an etching gas to form a second substrate product
Implementation Method 2
by depositing Si-based compound materials on the mesa structures during etching processes
Data Source
AI summary
A method for fabricating a light receiving device includes: preparing a first substrate product which includes a semiconductor region having a common semiconductor layer, a first semiconductor laminate for a photodiode, a second semiconductor laminate for a waveguide, and a butt-joint between the first semiconductor laminate and the second semiconductor laminate, the first laminate and the second semiconductor laminate being disposed on the common semiconductor layer; etching the first substrate product with a first mask to form a second substrate product having a photodiode mesa structure produced from the first semiconductor laminate and a preliminary mesa structure produced from the second semiconductor laminate; etching the second substrate product with the first mask and a second mask, formed on the photodiode mesa structure; to produce a waveguide mesa structure from the preliminary mesa structure, and the waveguide mesa structure having a height larger than that of the preliminary mesa structure.