AlGaN Insertion Layer for LED Buffer Stress Reduction
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Solution Overview
Problem
The challenge in fabricating miniaturized light emitting diodes (LEDs) is the occurrence of cracks, warpage, or dislocation in the semiconductor layer due to differences in lattice coefficient and thermal expansion between the semiconductor layer and the substrate, which leads to stress and defects.
Innovation Solution
Incorporating an aluminum (Al) insertion layer into the buffer layer between the substrate and the light emitting structure, specifically using aluminum nitride (AlN) as the first buffer layer and aluminum gallium nitride (AlGaN) as the insertion layer, to planarize the surface and reduce molecular diffusion and meltback, thereby minimizing defects and enhancing thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a semiconductor layer is formed on a substrate with different lattice coefficients, then light emitting device functionality is achieved, but cracks, warpage, or dislocation occur due to stress from lattice coefficient and thermal expansion differences
Solution Approach 1:
An insertion layer comprising aluminum gallium nitride (AlGaN) is introduced between the aluminum nitride (AlN) buffer layer and the light emitting structure. This intermediary layer has a lattice coefficient that gradually transitions from the buffer layer to the semiconductor layer, reducing the abrupt lattice mismatch and thermal expansion difference. This gradient structure minimizes stress concentration, preventing cracks, warpage, and dislocation while maintaining the functional integrity of the light emitting device.
2Illumination intensity
If the surface of the light emitting device is planarized, then light extraction efficiency is improved, but additional processing steps and structural complexity are required
Solution Approach 1:
The insertion layer is incorporated into the buffer structure during the epitaxial growth process, before the light emitting structure is formed. This preliminary action creates a pre-planarized surface that provides a flat template for subsequent semiconductor layer deposition. By establishing the planar surface early in the fabrication sequence, the need for additional post-growth planarization steps is eliminated, and the overall structural complexity is managed through integrated layer design rather than separate corrective processes.
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 effectively reduces dislocation and molecular diffusion, improves light extraction efficiency, and enhances the reliability and thermal stability of the light emitting device by planarizing the surface and preventing defects caused by lattice coefficient differences.
Implementation Method 1
reduces dislocation and molecular diffusion
Implementation Method 2
cracks, warpage or dislocation may occur in the semiconductor layer due to differences in lattice coefficient and coefficient of thermal expansion between the semiconductor layer and the substrate
Data Source
AI summary
Disclosed is a light emitting device including a substrate, a first buffer layer disposed on the substrate, the first buffer layer comprising aluminum nitride (AlN), an insertion layer disposed on the first buffer layer, the insertion layer comprising aluminum (Al), and a light emitting structure disposed on the insertion layer, the light emitting structure comprising a first semiconductor layer, a second semiconductor layer, and an active layer interposed between the first semiconductor layer and the second semiconductor layer.