Semiconductor Photoreceptor Device Reducing Pad Capacitance
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Solution Overview
Problem
Conventional semiconductor photoreceptor devices suffer from degradation in high-frequency response due to pad capacitance caused by silicon pile-up layers, leading to unfavorable eye patterns and reduced yield, especially at frequencies above 40 GHz.
Innovation Solution
A semiconductor photoreceptor device configuration with a semi-insulative semiconductor substrate, optical waveguide layer, and a lead-out portion extending on the side wall of the burying layer, connected to an electrode pad on the surface with an insulating film, which reduces pad capacitance by eliminating the silicon pile-up layer and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the diameter of the light receiving portion is reduced to reduce capacitance, then the response speed increases, but the light receiving efficiency decreases
Solution Approach 1:
The patent transitions from a planar photoreceptor structure to a waveguide-type three-dimensional structure. By confining light in the vertical dimension through waveguide layers and achieving lateral expansion of the effective light receiving area through the waveguide mode, the patent simultaneously reduces capacitance (smaller top electrode area) and maintains light receiving efficiency (enhanced light confinement and extended interaction length).
Solution Approach 2:
The patent employs a composite waveguide structure with multiple layers having different refractive indices (InP, InGaAsP, etc.) to confine and guide light. This composite material approach enables efficient light propagation and coupling while maintaining a compact structure with reduced capacitance, resolving the contradiction between speed and efficiency.
2Use of energy by moving object
If Zn is used as a p-type impurity in the waveguide layer, then the light absorption is enhanced, but Zn diffuses into the light absorption layer and blocking layer degrading device performance
Solution Approach 1:
The patent introduces an intermediary layer or barrier structure between the waveguide layer containing Zn and the light absorption layer. This intermediary prevents Zn diffusion while allowing optical properties to be maintained, thus preserving light absorption enhancement without the harmful diffusion effect that would degrade device performance.
Solution Approach 2:
The patent applies local quality control by using different impurity concentrations and types in different regions. The waveguide layer contains Zn for optimal optical properties, while the light absorption layer uses a different p-type impurity (such as Be or Mg) that does not diffuse from the waveguide, thereby maintaining both light absorption and device performance.
Data Source
AI summary
A semiconductor light detecting device includes an n-contact layer selectively disposed on an Fe—InP substrate. An optical waveguide layer is disposed on the n-contact layer and includes an n-cladding layer, a light absorption layer, and a p-cladding layer, laminated on one another, over the n-contact layer, in that order. An Fe—InP current blocking layer is disposed on the n-cladding layer such that sides of the optical waveguide layer are buried in the Fe—InP current blocking layer. A p-electrode includes a contact electrode electrically connected to the p-cladding layer of the optical waveguide layer, a lead-out electrode portion extending on a side wall of the current blocking layer from the contact electrode and extending on the Fe—InP substrate, and an electrode pad disposed on a surface of the Fe—InP substrate, with an SiN film between the electrode pad and the surface of the Fe—InP substrate and connected to the lead-out electrode portion.