Photodiode Waveguide Electrical Isolation via Modified Layer
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Solution Overview
Problem
In semiconductor optical devices, the integration of photodiodes and optical waveguides on a substrate faces challenges with electrical isolation, as conductive semiconductor layers within the waveguides allow for unintended electrical conduction paths between photodiodes, compromising signal conversion efficiency.
Innovation Solution
A semiconductor optical device is designed with a modified layer that forms a barrier for carriers, using a butt-joint configuration between the photodiode and optical waveguide layers, where the fourth layer has a shorter bandgap wavelength than the second layer, ensuring electrical isolation by preventing electrical coupling through the waveguide mesa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If photodiodes are integrated with optical waveguides on a substrate, then device integration and compactness are improved, but electrical isolation between photodiodes deteriorates due to conductive semiconductor layers in the waveguides creating unintended conduction paths
Solution Approach 1:
The optical waveguide structure is segmented into multiple layers with different electrical properties. The fourth layer (waveguide core) is made transparent to optical signals and electrically insulating, while the fifth layer (cladding) provides additional isolation. This segmentation allows the waveguide to be divided into optically functional regions and electrically isolating regions, preventing conduction paths between photodiodes while maintaining optical continuity.
Solution Approach 2:
Different layers of the waveguide structure are assigned different local qualities: the fourth layer has optical transparency and electrical insulation properties, while the fifth layer provides enhanced electrical isolation. The modified layer in the photodiode region has specific conduction properties, while the waveguide region has insulating properties. This local differentiation of material properties enables simultaneous optical functionality and electrical isolation.
2Reliability
If trenches are formed between photodiodes for electrical isolation, then electrical isolation is improved, but device complexity and manufacturing complexity increase
Solution Approach 1:
The electrical isolation function is merged into the waveguide structure itself through the fourth and fifth layers, rather than being implemented as separate trenches between photodiodes. The waveguide layers extend continuously across the substrate and provide electrical isolation as an inherent property of their material composition and layer configuration, eliminating the need for additional isolation structures.
Solution Approach 2:
The fourth and fifth layers of the waveguide structure serve multiple functions: they guide optical signals through the device, provide electrical isolation between photodiodes, and maintain structural integrity. This multi-functionality eliminates the need for separate isolation trenches, reducing device complexity while achieving the same electrical isolation effect.
3Reliability
If the fourth layer has a shorter bandgap wavelength than the second layer, then electrical isolation is improved by preventing carrier conduction, but optical transparency requirements must be balanced
Solution Approach 1:
The bandgap wavelength parameter of the fourth layer is specifically chosen to be shorter than that of the second layer. This parameter change ensures that the fourth layer is electrically insulating to carriers generated in the photodiode's absorption layer (second layer) while remaining transparent to the optical signals at the operating wavelength. The material composition and thickness of the fourth layer are optimized to achieve this dual requirement.
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 effectively isolates photodiodes electrically, preventing unwanted conduction paths and enhancing signal conversion efficiency by maintaining optical transparency and electrical insulation within the device.
Implementation Method 1
the modified layer forms a pn-junction against the first layer adjacent to the modified layer
Implementation Method 2
the fourth layer has a bandgap wavelength shorter than a band gap wavelength of the second layer, namely, the fourth layer is substantially transparent for an optical signal subject to the PD
Implementation Method 3
a plurality of photodiodes (PDs) that convert optical signals provided from the optical hybrid into electrical signals
Data Source
AI summary
A semiconductor optical device that integrates photodiodes (PDs) and optical waveguides coupling with the PDs and a method of forming the semiconductor optical device are disclosed. The optical waveguides in a portion in the lower cladding layer thereof provides a modified layer that forms a conduction barrier of the lower cladding layer. The modified layer is formed by converting the conduction type thereof or implanting protons therein. The modified layer prevents the electrical coupling between PDs through the waveguides.