Suspended GaN LED with Waveguide for Monolithic Integration
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Solution Overview
Problem
The integration of nitride photonic devices on silicon substrates faces challenges due to lattice mismatch and stress, hindering the development of high-quality nitride materials and optical microelectromechanical devices, especially with the complexity of combining different materials for LEDs and optical waveguides.
Innovation Solution
A monolithic photonic integration of a silicon substrate suspended light-emitting diode (LED) with an optical waveguide is achieved by using a silicon-based nitride wafer, featuring a silicon substrate layer, epitaxial buffer layer, P-N junction, and integrated optical waveguide, where the LED and waveguide are formed using the same nitride material, simplifying fabrication and reducing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nitride materials (GaN) are used for LED and optical waveguide fabrication, then optical performance is improved due to high refractive index and transparency, but manufacturing difficulty increases due to immature fabrication techniques and difficulty in manufacturing substrates
Solution Approach 1:
The patent combines the LED and optical waveguide into a single integrated device structure, where both components are fabricated using the same nitride material system on the same substrate. This merging approach allows simultaneous optimization of optical performance while simplifying the manufacturing process by eliminating the need for separate fabrication of discrete components and their subsequent assembly.
Solution Approach 2:
The patent employs composite nitride material structures, including InGaN/GaN quantum wells for light emission and AlN/GaN buffer layers for substrate compensation. These composite materials enable tailored optical and mechanical properties that balance high optical performance with manufacturability by compensating for thermal expansion mismatches and lattice defects.
2Adaptability or versatility
If different materials are used for LED and optical waveguide, then functional performance is improved, but device complexity increases due to need to combine different materials
Solution Approach 1:
The patent uses a universal nitride material platform (GaN-based) that serves multiple functions: the same material system is used for both the LED active region and the optical waveguide. This multi-functionality approach maintains functional performance by enabling light generation and light guidance within the same material ecosystem, while dramatically reducing device complexity by eliminating material interfaces and heterogeneous integration challenges.
Solution Approach 2:
The patent employs homogeneous nitride materials throughout the device structure, including InGaN/GaN quantum wells for light emission and AlN/GaN buffer layers for structural support. This homogeneity ensures consistent optical and electrical properties across the entire device, simplifying fabrication processes and reducing interface-related defects while maintaining high functional performance.
3Loss of energy
If silicon substrate is removed to create suspended structure, then light source utilization is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent extracts the silicon substrate from the final device structure by removing it through selective etching processes, leaving only the nitride-based LED and optical waveguide suspended on AlN/GaN buffer layers. This extraction eliminates light absorption and scattering by the silicon substrate, significantly improving light source utilization. The manufacturing precision is managed through carefully controlled etching parameters and buffer layer design that provide mechanical support during fabrication.
Solution Approach 2:
The patent performs preliminary actions by growing thick AlN/GaN buffer layers on the silicon substrate before device fabrication. These buffer layers serve as mechanical supports during the fabrication process and are later retained as part of the suspended structure. This preliminary preparation simplifies the subsequent substrate removal process and ensures manufacturing precision by providing a stable foundation throughout fabrication.
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 enhances light source utilization and efficiency by integrating the LED and optical waveguide on the same wafer, reducing internal losses and enabling scalable, cost-effective production of nitride optical devices for optical communication and sensing.
Implementation Method 1
The P-N junction comprises an n-GaN layer, an InGaN/GaN quantum well and a p-GaN layer that are sequentially connected from bottom to top
Implementation Method 2
an optical waveguide is integrated on the LED
Data Source
AI summary
By using various anisotropic silicon etching techniques, a silicon substrate layer (1) and an epitaxial buffer layer (2) under the device structure are removed to obtain a monolithic photonic integration of silicon substrate suspended light-emitting diode (LED) with optical waveguide, and an ultra-thin device monolithically integrated with a suspended LED and an optical waveguide is obtained by further using the nitride back thinning etching technique. Therefore, internal loss of the LED is reduced and light emitting efficiency is improved. In the device according to the present disclosure, the light source and the optical waveguide are integrated on the same wafer, which solves the problem of monolithic integration of planar photons, enables the light emitted by the LED to be transmitted along the optical waveguide, addresses the problem of transmission of light in the optical waveguide, and implements the function of transmitting light within a plane.