Si Waveguide Light-Receiving Element with Intrinsic Buffer
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Solution Overview
Problem
Existing semiconductor light-receiving elements integrated with Si waveguides face challenges in reducing dark current and achieving high photoelectric conversion efficiency due to lattice defects and high sensitivity degradation, particularly when using Ge absorption layers with different lattice constants from Si.
Innovation Solution
A semiconductor light-receiving element is designed with a Si waveguide structure comprising a first conductivity-type Si layer and an intrinsic Si layer, where a light-absorption layer made of Ge, SiGe, or a multi-layer film is stacked on the intrinsic Si layer, reducing lattice defects and dark current while enabling high sensitivity and efficient photoelectric conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a Ge light-absorption layer is integrated on Si waveguide, then photoelectric conversion efficiency is improved, but dark current increases due to lattice defects
Solution Approach 1:
An intrinsic Si layer is introduced as an intermediary between the Si waveguide and the Ge light-absorption layer. This intermediate layer acts as a buffer that reduces lattice mismatch defects while maintaining effective light absorption. The intrinsic Si layer allows carriers generated in the Ge layer to be efficiently collected without being depleted itself, thereby reducing dark current while preserving photoelectric conversion efficiency.
2Manufacturing precision
If intrinsic Ge layer is selectively grown on Si waveguide, then lattice defects are suppressed, but dark current increases when layer is depleted during operation
Solution Approach 1:
The conductivity type of the intermediate layer is changed from intrinsic Ge to intrinsic Si. This parameter change is crucial because Si has better lattice matching with the Si waveguide, reducing interface defects. Additionally, the intrinsic Si layer is not depleted during operation like the intrinsic Ge layer would be, thereby maintaining low dark current characteristics while still enabling efficient carrier collection from the Ge absorption layer.
3Productivity
If high voltage is applied to achieve APD operation, then photoelectric conversion efficiency is improved, but dark current increases due to high electric field on defective Ge layer
Solution Approach 1:
The intrinsic Si layer serves as an intermediary that enables high voltage application for APD operation without directly exposing the defective Ge layer to high electric fields. The intrinsic Si layer, having fewer defects and better lattice matching with Si, can withstand high electric fields with lower dark current generation. Carriers generated in the Ge layer are accelerated through the intrinsic Si layer where avalanche multiplication occurs, achieving high efficiency while minimizing dark current from the Ge layer.
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 solution results in a highly efficient semiconductor light-receiving element with low dark current and high integration capability with Si waveguides, enhancing reception sensitivity and durability under high power light conditions, while maintaining high speed responsiveness and reducing frequency degradation.
Implementation Method 1
highly efficient photoelectric conversion
Implementation Method 2
since the Ge has a different lattice constant from that of Si, when the light-absorption layer is integratedly formed on the Si, the dark current increases due to lattice defects or the like
Data Source
AI summary
The Si waveguide 305 includes a first conductivity-type Si layer 301 and an intrinsic Si layer 302, and a second conductivity-type light-absorption layer 303 is partially formed on an area thereof. During operation, a reverse bias is applied between the first conductivity-type Si layer 301 and the light-absorption layer 303. Since the light-absorption layer 303 has a conductivity type, it is not depleted when a voltage is applied, but the intrinsic Si layer 302 forming the Si waveguide 305 is depleted. Therefore, it is possible to reduce a CR time constant. Furthermore, since the intrinsic Si layer 302 can be formed on the first conductivity-type Si layer 301 in a continuous manner, it is possible to reduce lattice defects. As a result, it is possible to suppress the dark current generated in the light-receiving element.