Buried InP Optical Structure With Au Anti-Diffusion Layers
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Solution Overview
Problem
In optical semiconductor devices with a buried hetero-structure (BH) on an InP substrate, the diffusion of Au from the p-type electrode into the multiple-quantum well layer degrades the device's characteristics and reliability due to the high diffusion rate of Au in InP, which is difficult to completely prevent despite the use of Pt as a barrier layer.
Innovation Solution
Incorporating a first anti-diffusion layer with a smaller Au diffusion constant than InP, such as InGaAs, between the semi-insulating InP layers, and optionally a second anti-diffusion layer, to trap Au and prevent its diffusion into the active layers, thereby enhancing the device's reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Pt barrier layer is used to prevent Au diffusion, then Au diffusion is partially suppressed, but Au still diffuses into the multiple-quantum well layer through the burial layer due to surface shape effects
Solution Approach 1:
The single Pt barrier layer is segmented into multiple Pt layers separated by InP layers. This segmentation creates multiple diffusion barriers at different depths, preventing Au from reaching the multiple-quantum well layer even if the surface shape allows some diffusion paths. The segmented structure addresses the limitation of the single barrier layer by distributing the blocking function across multiple interfaces.
Solution Approach 2:
The burial layer is constructed as a composite structure combining InP layers with Pt barrier layers. This composite material approach leverages the high Au diffusion barrier properties of Pt while maintaining the semi-insulating and structural properties of InP. The composite structure provides superior Au diffusion prevention compared to using either material alone.
2Shape
If the p-type InGaAs contact layer is formed thin to achieve planar BH structure, then planarity is improved, but Au diffusion likelihood increases due to reduced diffusion path length
Solution Approach 1:
The contact layer structure is segmented into multiple thin InGaAs layers separated by InP layers. This segmentation maintains the overall thin profile needed for planarity while creating multiple Au diffusion barriers. Each InP layer acts as a discrete barrier, preventing Au from diffusing through the entire contact layer thickness to reach the multiple-quantum well layer.
Solution Approach 2:
The contact layer is formed as a composite structure of InGaAs and InP layers. The InGaAs provides good electrical contact properties while the embedded InP layers provide Au diffusion barriers. This composite approach maintains planarity through the thin overall structure while preventing Au diffusion through the multiple barrier interfaces.
3Reliability
If multiple Pt and InP layers are stacked to prevent Au diffusion, then Au diffusion is effectively blocked, but device structure complexity increases
Solution Approach 1:
The complex multi-layer structure is applied locally only to the burial layer region where Au diffusion prevention is most critical. The multiple Pt and InP layers are concentrated at the interfaces where Au diffusion paths are most likely to occur, while other regions of the device maintain simpler structures. This localized complexity approach prevents Au diffusion without unnecessarily complicating the entire device structure.
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 use of anti-diffusion layers significantly reduces Au diffusion, ensuring long-term reliability and maintaining high-frequency characteristics by effectively preventing Au from reaching the multiple-quantum well layer, thus improving the overall performance and durability of the optical semiconductor device.
Implementation Method 1
the diffusion of Au from the p-type electrode into the multiple-quantum well layer degrades the device's characteristics and reliability due to the high diffusion rate of Au in InP
Data Source
AI summary
To provide an optical semiconductor device having excellent long-term reliability, the optical semiconductor device includes: a substrate; a mesa structure provided on the substrate; a semiconductor burial layer provided in contact with two sides of the mesa structure; and an electrode containing Au, which is provided above the semiconductor burial layer. The mesa structure includes a first conductivity type semiconductor layer, a multiple-quantum well layer, and a second conductivity type semiconductor layer, which are stacked in the stated order from a substrate side. The semiconductor burial layer includes a first semi-insulating InP layer provided in contact with side portions of the mesa structure, a first anti-diffusion layer provided in contact with the first semi-insulating InP layer, and a second semi-insulating InP layer provided on the first anti-diffusion layer. The first anti-diffusion layer has an Au diffusion constant that is smaller than that of the first semi-insulating InP layer.