Recessed Germanium Photodetector on SOI Waveguides
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Solution Overview
Problem
Current p-i-n Ge photodetectors integrated on SOI waveguides exhibit large topographical variation and optical mode proximity to electrodes, leading to process complexity, high loss, and reduced optical sensitivity.
Innovation Solution
A method involving the formation of a recessed waveguide layer section by etching a trench in the detector region of a semiconductor substrate, followed by filling it with Ge to create a ridge structure photodetector, which reduces topographical variation and optical loss by offsetting electrodes and contacts from the waveguide layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If p-i-n Ge photodetectors are integrated on SOI waveguides, then quantum efficiency and responsivity are improved, but topographical variation increases and optical loss increases
Solution Approach 1:
The patent introduces a vertical dimension by etching a trench into the SOI waveguide substrate and forming a Ge layer within the trench. This vertical integration approach allows the photodetector to be embedded below the waveguide surface, separating the optical mode from the electrodes while maintaining efficient light-to-electricity conversion in the Ge layer.
Solution Approach 2:
The patent embeds the Ge photodetector structure within the SOI waveguide substrate by forming a trench and filling it with Ge material. The photodetector is nested inside the waveguide structure, with the Ge layer positioned within the trench and electrodes formed on the sides, creating a nested configuration that reduces topographical variation.
2Measurement precision
If p-i-n Ge photodetectors are integrated on SOI waveguides, then quantum efficiency is improved, but process complexity increases
Solution Approach 1:
By moving the photodetector integration to the vertical dimension through trench formation, the patent simplifies the lateral process steps. The Ge layer is deposited conformally in the trench, and electrodes are formed on the sidewalls, reducing the need for complex lateral alignment and reducing overall process complexity.
3Power
If electrodes and contacts are placed close to the waveguide for efficient electrical connection, then electrical performance is improved, but optical loss increases due to proximity to the optical mode
Solution Approach 1:
The patent resolves this contradiction by positioning electrodes on the sidewalls of the trench rather than directly adjacent to the waveguide surface. This vertical separation in the lateral dimension allows electrical contacts to be made to the Ge layer without the electrodes being in the immediate vicinity of the optical mode, thereby reducing optical loss while maintaining electrical connectivity.
Solution Approach 2:
The trench structure acts as an intermediary that separates the electrodes from the optical mode. The Ge layer within the trench serves as the active region for both optical absorption and electrical contact, mediating between the optical waveguide and the electrical electrodes, allowing efficient electrical connection without direct electrode proximity to the optical path.
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 reduces process complexity and enhances optical sensitivity by minimizing the proximity of electrodes and contacts to the waveguide, thereby decreasing optical loss and improving the performance of photodetectors integrated on waveguides.
Implementation Method 1
light at the silicon-silica interface will undergo total internal reflection and remain in the silicon
Implementation Method 2
p-i-n Ge photodetectors exhibit good responsivity and quantum efficiency for optical absorption
Data Source
AI summary
Semiconductor devices and methods for fabricating semiconductor devices are provided. In one example, a method for fabricating a semiconductor device includes etching a waveguide layer in a detector region of a semiconductor substrate to form a recessed waveguide layer section. A ridge structure germanium (Ge) photodetector is formed overlying a portion of the recessed waveguide layer section.