Rib Waveguide Schottky Photodetector with Sidewall Metal Contact
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Solution Overview
Problem
Conventional Schottky photodetectors on silicon substrates have low responsivity due to limited photon absorption by the metal layer, leading to contamination issues and incompatibility with dense silicon photonics integrated circuits, especially when using gold electrodes.
Innovation Solution
A rib waveguide-based Schottky photodetector with a metal contact layer that directly abuts the uppermost and sidewall surfaces of the waveguide, made from non-gold materials like titanium, tungsten, or platinum, which reduces contamination risks and enhances operational bandwidth by forming a Schottky barrier with a doped silicon waveguide, increasing absorption efficiency through a plasmonic waveguide structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Schottky photodetectors use metal layer to absorb photons, then photodetector function is achieved, but responsivity is extremely low due to limited photon absorption
Solution Approach 1:
The metal contact layer is configured to wrap around the silicon waveguide, contacting the top surface and sidewalls simultaneously. This three-dimensional contact structure increases the effective photon absorption area from a single top surface to multiple surfaces including sidewalls, thereby significantly improving responsivity without increasing the metal material quantity
Solution Approach 2:
The metal contact layer is divided into multiple contact regions along the waveguide length, with each segment contributing to photon absorption. This segmentation allows the optical mode to interact with metal at multiple positions, enhancing overall absorption efficiency while maintaining a manageable device structure
2Object-generated harmful factors
If gold electrodes are used to make Schottky contact, then electrical contact is achieved, but contamination issues arise for other silicon devices
Solution Approach 1:
The patent replaces expensive and contaminating gold electrodes with alternative metals such as titanium, tungsten, or platinum. These alternative materials provide the necessary electrical contact function without the contamination issues associated with gold, making them suitable for dense silicon photonics integrated circuits
Solution Approach 2:
The Schottky barrier height is optimized by selecting appropriate metal materials with specific work functions. Titanium, tungsten, and platinum provide suitable barrier heights for photodetector operation while avoiding gold-related contamination, thus changing the material parameter to resolve the contradiction
3Ease of manufacture
If metal contact layer contacts only top of waveguide, then fabrication is simple, but optical mode mismatch is large with only 62% coupling efficiency
Solution Approach 1:
The metal contact layer extends from the top surface onto the sidewalls of the waveguide, creating a three-dimensional contact structure. This dimensional extension improves optical mode coupling by providing additional interaction surfaces between the metal and optical mode, achieving over 92% coupling efficiency while maintaining fabrication simplicity through conformal deposition techniques
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 achieves high responsivity and reduces contamination risks, enabling efficient photon absorption with >92% coupling efficiency and compatibility with silicon photonics integrated circuits, while avoiding gold-related issues.
Implementation Method 1
a Schottky photodetector utilizing the internal photo-emission effect (IPE)
Implementation Method 2
provide a Schottky barrier between the metal contact layer and the rib waveguide
Data Source
AI summary
An optoelectronic device, and a method of fabricating an optoelectronic device. The device comprising: a rib waveguide formed of doped silicon, said doped waveguide having a ridge portion, containing an uppermost surface and two sidewall surfaces; and a slab portion, adjacent to the two sidewall surfaces. The device further comprises: a metal contact layer, which directly abuts the uppermost surface and two sidewall surfaces, and which extends along a part of the slab portion so as to provide a Schottky barrier between the metal contact layer and the rib waveguide.