Nitride Semiconductor Light-Emitting Device With Porous Buffer Layer
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Solution Overview
Problem
Light-emitting devices face degradation in light extraction efficiency due to the high refractive index of nitride semiconductors and residual stress caused by lattice constant differences between the InGaN active layer and the GaN-based current injection layer.
Innovation Solution
A light-emitting device with a porous structure featuring voids in the buffer layer is developed, which enhances light extraction efficiency and reduces residual stress by forming a concave-convex structure on the substrate and incorporating a stress-reducing layer with low InGaN content under the active layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high refractive index nitride semiconductor is used, then the light-emitting device can achieve efficient light generation, but light extraction efficiency is degraded
Solution Approach 1:
The patent introduces a porous buffer layer with controlled voids between the substrate and the light-emitting structure. This porous structure creates refractive index gradients and scattering centers that enable light trapped by total internal reflection to escape, thereby improving light extraction efficiency without compromising the high refractive index nitride semiconductor's light generation capability
Solution Approach 2:
The patent adds a vertical dimension to light extraction by creating voids that extend through the buffer layer thickness. This three-dimensional porous structure provides additional light extraction pathways in the vertical direction, complementing the in-plane light generation and improving overall extraction efficiency
2Illumination intensity
If an InGaN active layer is used to achieve desired emission characteristics, then light emission can be optimized, but residual stress occurs due to lattice constant difference with GaN-based current injection layer
Solution Approach 1:
The patent introduces a porous buffer layer as an intermediary structure between the substrate and the InGaN active layer. This buffer layer acts as a stress management interface that accommodates the lattice mismatch between different nitride layers, reducing residual stress while allowing the InGaN active layer to maintain its optimized emission characteristics
Solution Approach 2:
The patent modifies the physical and structural parameters of the buffer layer by creating a porous structure with controlled void density, size, and distribution. These parameter changes enable the buffer layer to mechanically accommodate stress while maintaining its functional role in supporting the light-emitting structure
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 improves light extraction efficiency and reliability by scattering light and mitigating stress in the nitride semiconductor, thereby enhancing the overall performance of the light-emitting device.
Implementation Method 1
The buffer layer may include a plurality of voids, the plurality of voids extending vertically into the buffer layer from a surface of the buffer layer, the surface proximate to the light-emitting structure
Data Source
AI summary
A light-emitting device includes a light-emitting structure including a first-conductivity-type nitride semiconductor layer on a substrate, an active layer on the first-conductivity-type nitride semiconductor layer, and a second-conductivity-type nitride semiconductor layer on the active layer, and a buffer layer between the substrate and the light-emitting structure. The buffer layer includes a plurality of voids. The plurality of voids extend vertically into the buffer layer from a surface of the buffer layer. The surface of the buffer layer is proximate to the light-emitting structure. The plurality of voids have different horizontal sectional areas.