Waveguide Photodetector Buried-Layer Structure for Shorter Window Length
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Solution Overview
Problem
Conventional waveguide-type light-receiving elements with a semiconductor buried layer structure face issues with increased window length, leading to decreased photosensitivity due to light leakage and absorption, making it difficult to achieve high-speed and high-sensitivity performance.
Innovation Solution
The structure includes a ridge waveguide with a light absorption layer buried by a semiconductor buried layer, where the light incident end surface is precisely controlled through etching, allowing for a shorter window length and improved positional accuracy, enhancing photosensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the light absorption layer is buried by a semiconductor buried layer, then heat dissipation is improved, but the window length increases leading to decreased photosensitivity
Solution Approach 1:
The semiconductor buried layer is segmented into a first semiconductor buried layer and a second semiconductor buried layer. The first layer has a first refractive index and the second layer has a second refractive index different from the first. This segmentation allows independent optimization of each layer's thickness and refractive index to balance heat dissipation and photosensitivity. The first layer primarily provides thermal management while the second layer is optimized for optical confinement, resolving the contradiction between heat dissipation requirements and window length control.
Solution Approach 2:
Different regions of the semiconductor buried layer structure are assigned different local properties. The first semiconductor buried layer is positioned closer to the light incident end surface and optimized for optical properties (refractive index matching), while the second semiconductor buried layer is positioned deeper and optimized for thermal conductivity. This local quality differentiation allows the structure to simultaneously achieve good heat dissipation and maintain short effective window length for high photosensitivity.
2Reliability
If the window length is increased to accommodate cleavage variation, then manufacturing robustness is improved, but light leakage and absorption increase decreasing photosensitivity
Solution Approach 1:
The invention changes the optical parameters (refractive indices) of the semiconductor buried layers to optimize light confinement. By setting specific refractive index relationships (first layer refractive index closer to light absorption layer, second layer refractive index lower), the structure achieves superior light confinement compared to conventional single-layer designs. This allows the window length to be minimized while maintaining manufacturing robustness, as the optimized optical parameters compensate for cleavage variations.
Solution Approach 2:
The semiconductor buried layer is constructed as a composite structure with two different semiconductor materials having different refractive indices. This composite approach enables simultaneous optimization of optical confinement and thermal management functions. The first semiconductor material provides better optical matching to reduce light leakage, while the second material provides thermal management, together achieving both manufacturing robustness and high photosensitivity.
3Device complexity
If a single semiconductor buried layer is used, then device complexity is reduced, but photosensitivity is insufficient due to light leakage
Solution Approach 1:
The semiconductor buried layer is divided into two distinct layers with different refractive indices and functions. The first semiconductor buried layer is positioned adjacent to the light absorption layer and optimized for optical confinement with a refractive index closer to that of the light absorption layer. The second semiconductor buried layer is positioned deeper and optimized for thermal management with lower refractive index. This segmentation effectively reduces light leakage while maintaining manageable device complexity through systematic layer design.
Solution Approach 2:
The two-layer semiconductor buried layer structure performs multiple functions simultaneously: the first layer provides optical confinement to prevent light leakage, the second layer provides thermal management, and together they provide mechanical support and electrical isolation. This multi-functionality achieves high photosensitivity without proportionally increasing device complexity, as the layers are integrated into the existing device architecture.
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 approach results in waveguide-type light-receiving elements with stable and high photosensitivity, manufactured with high reproducibility, by controlling the window length and reducing light leakage and absorption, thus improving the element's performance.
Implementation Method 1
light is guided to a light absorption layer formed at a position several μm or more away from the incident portion, and evanescent light leaking from the guide layer in the layer thickness direction is photoelectrically converted in the light absorption layer
Implementation Method 2
an optical waveguide is formed up to cleaved end surfaces. Light is made incident on the optical waveguide, light is guided to a light absorption layer
Data Source
AI summary
A waveguide-type light-receiving element of the present disclosure includes: a semiconductor substrate; a ridge waveguide including a first-conductivity-type contact layer, a first-conductivity-type cladding layer, a light absorption layer, and a second-conductivity-type cladding layer, which are laminated above the semiconductor substrate, the ridge waveguide having a light incident surface separated from one end of the semiconductor substrate and a rear surface separated from the other end of the semiconductor substrate; a first semiconductor buried region provided in contact with the light incident surface and having a light incident end surface that is one surface on a light incident side and is separated from the one end of the semiconductor substrate; and a second semiconductor buried region provided in contact with the rear surface and having a rear end surface that is one surface facing the rear surface and is separated from the other end of the semiconductor substrate.