Integrated Gain Element With Decoupled Current and Optical Confinement
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Solution Overview
Problem
Current semiconductor technologies face challenges in monolithically integrating reliable and manufacturable modulators with lasers and optical amplifiers, particularly due to issues with current confinement and optical coupling between strongly guided and weakly guided waveguides, as well as unintentional growth enhancement in Selective Area Epitaxy (SAE) processes.
Innovation Solution
The integration of a semiconductor device using Selective Area Epitaxy with a mask to suppress or enhance growth at the edges, combined with a deeply-etched ridge waveguide modulator, allows for independent control of current and optical confinement, enabling efficient coupling between the modulator and optical amplifier without introducing additional optical elements, and utilizes variable mask profiles to prevent unwanted growth enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Selective Area Epitaxy (SAE) growth is used to integrate modulator with laser and optical amplifier, then monolithic integration is achieved, but unintentional growth enhancement occurs at mask edges
Solution Approach 1:
The patent applies local quality by modifying the mask edge geometry specifically at the regions where growth enhancement occurs. The mask features varied edge profiles including angled, curved, or tapered edges at critical locations, while maintaining straight edges in non-critical areas. This localized modification suppresses unintentional growth enhancement at mask edges while preserving the overall monolithic integration capability of SAE.
Solution Approach 2:
The patent changes the geometric parameters of the mask edges to control growth patterns. By adjusting edge angles, curvature radii, and taper ratios, the patent optimizes the epitaxial growth process to minimize enhancement effects. Specific parameter ranges are provided for mask edge angles (e.g., 45-60 degrees) and curvature radii to achieve uniform growth while maintaining manufacturing feasibility.
2Reliability
If deeply-etched ridge waveguide structure is used, then optical confinement is improved, but current confinement becomes difficult to control independently
Solution Approach 1:
The patent segments the waveguide structure into distinct functional regions: a deeply-etched ridge waveguide section for optimal optical confinement, and adjacent regions with modified etch depths or material compositions for current confinement. This segmentation allows each region to be optimized independently - the ridge section provides strong optical guiding while the adjacent regions provide current injection control without interfering with optical modes.
Solution Approach 2:
The patent introduces an additional dimensional degree of freedom by varying the lateral width profile of the ridge waveguide. In addition to the vertical etch depth, the ridge width is modulated along the propagation direction, creating a width-tapered structure. This width variation provides an independent control mechanism for current distribution while maintaining the optical confinement provided by the deep etch, thereby decoupling the two functions.
3Manufacturing precision
If variable mask profiles are used to suppress growth enhancement, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies partial modification to the mask structure, using variable edge profiles only in the specific regions where growth enhancement is problematic, while maintaining simple straight edges in other regions. This partial application of complexity achieves the necessary growth control without requiring the entire mask structure to be complicated, thereby balancing manufacturing precision with device complexity.
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 provides better current confinement and electrical efficiency, reduces manufacturing complexity and cost, and enhances the reliability of the semiconductor device by decoupling current and optical confinement, allowing for efficient light coupling between the modulator and gain section.
Implementation Method 1
perform Selective Area Epitaxy (SAE) growth on the semiconductor wafer
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
A photonic integrated circuit including a photonic device and a gain element, said gain element formed by a process including: depositing by epitaxy a first doped layer onto a substrate; depositing by epitaxy an active layer capable of optical gain onto the first doped layer; depositing by epitaxy a second doped layer onto the active layer; pattern etching at least the second doped layer and the active layer to form a first ridge; and depositing by epitaxy a current blocking layer laterally adjacent to the first ridge at least partially filling the volume of active layer that was removed by the pattern etching; wherein the current blocking layer forms a portion of the photonic device.