Germanium-Doped Optical Waveguide Detector Bandwidth
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Solution Overview
Problem
Current silicon photonics interconnect systems, specifically lateral PIN (LPIN) optical waveguide detectors, have a relatively weak electric field distribution in the germanium waveguide, leading to low bandwidth and high dark current, which limits their performance in high-speed optical communications.
Innovation Solution
The introduction of a heavily germanium-doped area on the germanium waveguide, equivalent to providing an electrode, forms a PN junction with a counter electrode on the silicon waveguide, enhancing electric field strength and increasing the migration rate of photo-generated carriers, thereby increasing the bandwidth of the optical waveguide detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lateral PIN (LPIN) optical waveguide detector is used, then the device can convert optical signals into electrical signals, but the electric field distribution in the germanium waveguide is relatively weak, resulting in low bandwidth
Solution Approach 1:
The patent applies local quality by creating a heavily germanium-doped area specifically at one end of the germanium waveguide, rather than uniform doping throughout. This localized heavy doping concentrates the electric field generation at the critical region where optical signals enter, enhancing the electric field strength precisely where needed to improve bandwidth while maintaining other performance characteristics.
Solution Approach 2:
The patent changes the doping parameter of germanium from uniform or light doping to heavy doping in a specific region. By adjusting the doping concentration parameter to be heavily doped (with doping concentration greater than 1×10^19 atoms/cm³) in the first heavily germanium-doped area, the electric field generation capability is significantly enhanced, directly addressing the bandwidth limitation.
2Object-generated harmful factors
If a lateral PIN (LPIN) optical waveguide detector is used, then the device structure is relatively simple, but dark current is relatively high
Solution Approach 1:
The patent reduces dark current by applying local quality through asymmetric doping: heavily doping germanium at one end (first heavily germanium-doped area) while keeping the other end lightly doped or undoped. This creates an asymmetric electric field distribution that efficiently collects photo-generated carriers while minimizing thermal carrier generation, thereby reducing dark current without requiring complex additional structures.
Solution Approach 2:
The patent applies partial action by heavily doping only a portion of the germanium waveguide (the first heavily germanium-doped area with width less than or equal to half the waveguide width) rather than the entire waveguide. This partial heavy doping is sufficient to generate the required electric field for carrier collection while avoiding excessive doping that would increase dark current, achieving an optimal balance.
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 solution effectively enhances the electric field strength in the germanium waveguide, increasing the bandwidth and reducing dark current, meeting the requirements of high-speed optical communications systems while maintaining low optical loss.
Implementation Method 1
The electrode on the germanium waveguide and a counter electrode on a silicon waveguide may form a PN junction. This can enhance electric field strength in the germanium waveguide
Implementation Method 2
The PN junction is located below a germanium waveguide, and can generate an electric field in the germanium waveguide
Implementation Method 3
Because germanium can absorb an optical signal, a photo-generated carrier is generated in the germanium waveguide under action of the electric field
Data Source
Figure 1~2(d)
Figure 3~4
Figure 5~6
AI summary
An optical waveguide detector and an optical module are disclosed. The optical waveguide detector includes: a waveguide layer (2), an upper cladding layer (3), and an electrode layer (5) that are stacked in a first direction. The waveguide layer (2) includes a silicon waveguide layer (21) and a germanium waveguide layer (22). The germanium waveguide layer (22) is located between the silicon waveguide layer (21) and the upper cladding layer (3). The silicon waveguide layer (21) includes a P-type heavily silicon-doped area (211), a P-type lightly silicon-doped area (212), an N-type lightly silicon-doped area (214), and an N-type heavily silicon-doped area (213) that are arranged in a second direction, and the second direction is perpendicular to the first direction. The germanium waveguide layer (22) includes a first heavily germanium-doped area (222) and a germanium-undoped area (221). A first surface (U) of the germanium waveguide layer (22) includes a surface of the first heavily germanium-doped area (222), and the first surface (U) is a surface of the germanium waveguide layer (22) away from the silicon waveguide layer (21) in the first direction. A width of the first heavily germanium-doped area (222) is less than or equal to half a width of the first surface (U), and a thickness of the first heavily germanium-doped area (222) is greater than or equal to 5 nm and less than or equal to 200 nm. The upper cladding layer includes a metal through-hole (42) that connects the first heavily germanium-doped area (222) to the electrode layer (5). According to embodiments, a bandwidth of the optical waveguide detector can be effectively increased.