Semiconductor Optical Waveguide Layout for Differential Modulation
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Solution Overview
Problem
Conventional semiconductor devices integrated on conductive substrates cannot achieve differential modulation driving due to shared common potential, leading to impaired flatness and crystal quality of semiconductor layers, resulting in waveguide loss during electrode separation on semi-insulating substrates.
Innovation Solution
A semiconductor device is fabricated using a semi-insulating compound semiconductor substrate with optically connected waveguide type first and second optical elements, where each element has specific conductivity type layers and active layers, and a semi-insulating compound semiconductor cladding forms an optical waveguide, allowing for electrical separation without waveguide loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conductive substrate is used for monolithic integration, then device integration is achieved, but differential modulation driving cannot be realized due to common potential
Solution Approach 1:
The substrate is divided into first and second element regions with different conductivity types (n-type and p-type), allowing independent electrical control of each optical element region while maintaining monolithic integration
Solution Approach 2:
Different regions of the substrate are assigned different conductivity types and potential controls, enabling localized electrical separation and differential modulation driving in specific areas while maintaining overall integration
2Reliability
If electrode separation is performed on semi-insulating substrate by butt joint process, then electrical separation is achieved, but flatness of semiconductor layers is impaired
Solution Approach 1:
The core layer is formed in the separation region before the active layers, establishing a reference level that guides subsequent layer formation and ensures flatness is maintained throughout the stacking process
Solution Approach 2:
The core layer acts as a leveling layer that compensates for height differences between stacked semiconductor layers, creating an equipotential surface that maintains flatness for subsequent active layer formation
3Productivity
If active layer is grown on impaired flatness, then device fabrication continues, but in-plane uniformity and crystal quality are deteriorated
Solution Approach 1:
The core layer is formed in advance in the separation region to establish a flat reference surface before active layers are deposited, preventing flatness impairment from propagating to subsequent layers
Solution Approach 2:
The core layer serves as a cushioning layer that absorbs and compensates for flatness variations in the stacked semiconductor layers, protecting the active layers from inheriting these defects and maintaining crystal quality
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 enables effective electrical separation between optical elements, improving the S/N ratio and reducing common mode noise by allowing differential modulation driving without waveguide loss.
Implementation Method 1
a substrate including a semi-insulating compound semiconductor
Implementation Method 2
an optical waveguide formed in a separation region between the first element region and the second element region of the substrate, for optically connecting the first optical element and the second optical element
Implementation Method 3
a first semiconductor layer including a compound semiconductor of a first conductivity type that is formed on the substrate; a second semiconductor layer including a compound semiconductor of a second conductivity type that is formed on the first active layer
Data Source
AI summary
In an embodiment semiconductor device, a first optical element, a second optical element, and an optical waveguide for optically connecting the first optical element and the second optical element are provided on a substrate including a semi-insulating compound semiconductor. The first optical element is formed in a first element region of the substrate. The second optical element is formed in a second element region of the substrate. The optical waveguide is formed in a separation region between the first element region and the second element region of the substrate. The optical waveguide is configured by a cladding including a semi-insulating compound semiconductor on the substrate and a core including a compound semiconductor buried in the cladding.