Laser Diode Epitaxial Channel Structure for Lower GaN Dislocation
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Solution Overview
Problem
The existing methods for manufacturing GaN-based materials on mainstream epitaxial substrates result in high dislocation densities, which hinder the development of high-voltage resistant power devices and LEDs with longer wavelength bands.
Innovation Solution
A structure and method involving a base with a first and second mask layer, where the first mask layer has a channel with a smaller open end area compared to its cross-sectional area, and a second mask layer with a connected channel, facilitating epitaxial growth to reduce dislocation density by terminating dislocation extensions within the first channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If GaN-based materials are epitaxially grown on mainstream GaN-based epitaxial substrate using traditional MOCVD mode, then the manufacturing process is simple and mature, but the dislocation surface density is high (about 1-3E8/cm³)
Solution Approach 1:
The patent divides the epitaxial growth process into two distinct stages: first growing GaN-based material in the first channel to fill it completely, then removing the first mask layer and continuing growth in the second channel. This segmentation allows dislocations to be terminated at the first channel-masking layer interface, preventing them from propagating to the final product and achieving low dislocation density (below 1E8/cm³) while using standard MOCVD equipment.
Solution Approach 2:
The patent performs preliminary action by first forming the first mask layer with the first channel before epitaxial growth, and intentionally filling the first channel with GaN-based material in a controlled manner. This preliminary structure serves as a dislocation termination zone, allowing subsequent growth in the second channel to produce high-quality low-dislocation GaN-based material without requiring complete process redesign.
2Manufacturing precision
If the first channel has a smaller open end area compared to its cross-sectional area, then dislocation extension is terminated effectively, but the channel geometry becomes more complex
Solution Approach 1:
The patent employs asymmetric channel geometry where the first channel's open end area is deliberately made smaller than its cross-sectional area. This asymmetric design creates a geometric constraint that effectively terminates dislocation extensions while maintaining manufacturability through standard etching processes. The asymmetric shape is optimized to provide dislocation termination functionality without excessive geometric complexity.
3Productivity
If the second channel is connected to the first channel, then continuous epitaxial growth is enabled, but the risk of dislocation propagation increases
Solution Approach 1:
The patent introduces the first mask layer as an intermediary structure between the first and second channels. This mask layer acts as a dislocation barrier that prevents defect propagation while allowing the second channel to be connected to and grow from the first channel. The intermediary mask layer enables continuous epitaxial growth productivity while maintaining manufacturing precision by blocking dislocation pathways.
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 effectively lowers the dislocation density of GaN-based materials, enhancing the performance of GaN-based power devices and LEDs by improving crystal orientation and reducing threading dislocations.
Implementation Method 1
a first epitaxial sub-layer is epitaxially grown from the base to fully fill the first channel
Implementation Method 2
a second epitaxial sub-layer is epitaxially grown, from the first epitaxial sub-layer located at the first open end, in the second channel
Data Source
AI summary
A structure includes a base; a first mask layer disposed on the base, where the first mask layer has a first channel exposing the base, the first channel comprises a first open end and a second open end, the second open end is close to a surface of the base, the first open end is away from the surface of the base, and an area of an orthographic projection of the first open end in a plane where the base is located is smaller than an area of an orthographic projection of the first channel in the plane; and a second mask layer disposed on the first mask layer, where the second mask layer has a second channel exposing the first mask layer, and the second channel is connected to the first channel.