Recessed Germanium Avalanche Photodetector on SOI Waveguide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current silicon-based avalanche photodetector diodes integrated on silicon-on-insulator (SOI) waveguides suffer from topographical variation, process complexity, high loss, and reduced optical sensitivity, particularly in the near-infrared range due to inadequate light absorption.
Innovation Solution
A semiconductor device is fabricated by etching a trench into the waveguide layer to form a recessed waveguide section with dual multiplication regions and a germanium absorption region, reducing topographical variation and increasing optical sensitivity through lateral spacing of n-wells and P+ electrodes, thereby enhancing multiplication gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If germanium absorption region is integrated on SOI waveguide, then optical sensitivity is improved, but topographical variation increases
Solution Approach 1:
The patent transitions from planar integration to three-dimensional integration by etching a trench into the waveguide layer and placing the germanium absorption region within it. This vertical arrangement allows the absorption region to be recessed below the waveguide plane, reducing topographical variation while maintaining optical coupling efficiency through evanescent field interaction.
Solution Approach 2:
The germanium absorption region is nested within the etched trench structure of the waveguide layer. This nesting approach allows the absorption region to be embedded in the waveguide substrate, minimizing surface height differences and reducing topographical variation while preserving the optical interaction between the waveguide mode and the germanium absorption region.
2Measurement precision
If germanium absorption region is integrated on SOI waveguide, then optical sensitivity is improved, but process complexity increases
Solution Approach 1:
The device is segmented into distinct functional regions: the SOI waveguide layer for light transmission, the etched trench for structural organization, and the germanium absorption region for photon detection. This segmentation allows each component to be optimized independently and integrated through standard semiconductor fabrication processes, managing overall process complexity.
Solution Approach 2:
The germanium absorption region is localized within a specific trench structure rather than being uniformly distributed. This local concentration of optical absorption functionality improves optical sensitivity at the detection region while allowing other areas to maintain simple waveguide structures, thereby balancing performance improvement with process complexity management.
3Measurement precision
If germanium absorption region is integrated on SOI waveguide, then optical sensitivity is improved, but optical loss increases
Solution Approach 1:
The evanescent field of the waveguide mode acts as an intermediary that couples optical energy from the silicon waveguide to the germanium absorption region without requiring direct physical contact or high-loss interfaces. This field-mediated energy transfer enables efficient optical coupling while minimizing insertion loss.
Solution Approach 2:
By positioning the germanium absorption region in a recessed trench below the waveguide plane, the design utilizes the vertical dimension to optimize optical coupling. The evanescent field extends into the trench region, enabling efficient energy transfer to the germanium while maintaining the waveguide's low-loss transmission characteristics in the horizontal plane.
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 approach results in reduced topographical variation, lower optical loss, and improved optical sensitivity and multiplication gain, addressing the limitations of existing Ge APDs on SOI waveguides.
Implementation Method 1
An APD is a highly sensitive semiconductor electronic device that exploits the photoelectric effect to convert light to electricity
Implementation Method 2
By applying a high reverse bias voltage, e.g., typically about 100 to about 200 V in silicon (avalanche phenomenon as such could be started at as low a voltage as 10V depending upon the diode design), APDs show an internal current gain effect of up to about 100 due to impact ionization (avalanche effect)
Implementation Method 3
silicon is not suitable for photodetectors for optical applications using a wavelength ranging from 1.3 to 1.6 μm due to a lack of light absorption of silicon in the near infrared range. One solution is combining a germanium (Ge) layer on top of a silicon (Si) layer because of the high optical absorption of Ge
Implementation Method 4
silica is used as an intervening material because of its much lower refractive index, about 1.44 in the wavelength region of interest, than silicon and thus, light at the silicon-silica interface will undergo total internal reflection and remain in the silicon
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 trench into a waveguide layer in a detector region of a semiconductor substrate. An avalanche photodetector diode is formed about the trench. Forming the avalanche photodetector diode includes forming a multiplication region in the waveguide layer laterally adjacent to the trench. An absorption region is formed at least partially disposed in the trench.