InP Buffer Layer Sb Grading for InGaAs Surface Flatness
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Solution Overview
Problem
Existing semiconductor laminates for light-receiving elements, particularly those using III-V compound semiconductors, face challenges in achieving good crystallinity and surface flatness of the InGaAs buffer layer, which affects the performance of the light-receiving element.
Innovation Solution
A semiconductor laminate structure is developed with an InP substrate, a first InP buffer layer containing a higher concentration of Sb, and a second InGaAs buffer layer with a lower Sb concentration, where the first layer is formed with a high Sb concentration to improve surface flatness, and the second layer is formed on top of the first buffer layer to reduce unnecessary Sb concentration, resulting in excellent surface flatness and crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional InP substrate and InGaAs buffer layer structure is used, then the light-receiving element can be manufactured, but the surface flatness and crystallinity of the InGaAs buffer layer are insufficient
Solution Approach 1:
The buffer layer is divided into multiple distinct layers: an InP buffer layer and an InGaAs buffer layer, each with specific thickness ranges (InP: 1-10 nm, InGaAs: 10-100 nm). This segmentation allows each layer to perform its specific function independently, with the InP layer providing a crystalline foundation and the InGaAs layer providing surface flatness, thereby resolving the contradiction between manufacturing precision and structural complexity.
Solution Approach 2:
Different regions of the buffer layer structure are assigned different material compositions and properties. The InP buffer layer near the substrate provides excellent crystallinity, while the InGaAs buffer layer at the surface provides superior flatness. This local differentiation of material properties allows the structure to simultaneously achieve both crystallinity and surface flatness without excessive complexity.
2Manufacturing precision
If the InGaAs buffer layer is formed directly on the InP substrate, then the manufacturing process is simple, but the surface flatness is poor
Solution Approach 1:
An InP buffer layer is formed first as a preliminary step before depositing the InGaAs buffer layer. This preliminary InP layer serves as an intermediate foundation that prepares the substrate surface, improving the subsequent surface flatness of the InGaAs layer. Although this adds a step to the manufacturing process, it significantly enhances the final surface quality.
Solution Approach 2:
The InP buffer layer acts as an intermediary between the InP substrate and the InGaAs buffer layer. This intermediate layer mediates the interface between substrate and buffer, providing a transition zone that improves surface flatness and reduces direct interface defects, thereby resolving the contradiction between manufacturing simplicity and surface quality.
3Manufacturing precision
If Sb is added to improve surface flatness, then surface flatness improves, but dark current increases
Solution Approach 1:
Sb is added locally and selectively to specific layers (InP buffer layer and optionally InGaAs buffer layer) rather than uniformly throughout the entire structure. By controlling the spatial distribution and concentration of Sb in specific regions, the surface flatness is improved while limiting the generation of harmful effects like increased dark current in other regions.
Solution Approach 2:
The concentration of Sb is precisely controlled and varied across different layers. The InP buffer layer contains Sb at a first concentration, while the InGaAs buffer layer contains Sb at a second concentration (which may be lower or zero). By changing the Sb concentration parameter across different layers, the patent achieves surface flatness improvement while managing the trade-off with dark current generation.
Data Source
AI summary
A semiconductor laminate includes a substrate composed of InP, a first buffer layer composed of InP containing less than 1×1021 cm−3 Sb and disposed on the substrate, and a second buffer layer composed of InGaAs and disposed on the first buffer layer. The first buffer layer includes a first layer that has a higher concentration of Sb than the substrate and that is arranged to include a first main surface which is a main surface of the first buffer layer on the substrate side. The second buffer layer includes a second layer that has a lower concentration of Sb than the first layer and that is arranged to include a second main surface which is a main surface of the second buffer layer on the first buffer layer side.