Patterned InAlGaN Seed Regions for Relaxed Multi-Color InGaN Epitaxy
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Solution Overview
Problem
Current methods for growing high-quality, relaxed InGaN layers for optoelectronic devices face challenges such as severe strain and poor material quality due to lattice mismatch, leading to high defect densities and limited lattice dilation, which hinders the performance of LEDs and LDs.
Innovation Solution
A semiconductor structure is developed with patterned seed regions and growth layers, allowing for the growth of InxAlyGa1-x-yN layers with varying in-plane a-lattice parameters, enabling the formation of relaxed, device-quality InGaN regions suitable for multi-color optoelectronic devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If InGaN is grown pseudomorphically on GaN to maintain lattice matching, then device quality is maintained, but severe strain and high defect densities occur due to lattice mismatch
Solution Approach 1:
The patent divides the growth substrate into multiple patterned seed regions with different compositions (InGaN, AlGaN, InAlGaN) that are spatially separated. Each seed region serves as an independent nucleation site, allowing the overlying InxAlyGa1-x-yN layer to relax locally without generating excessive strain across the entire structure. This segmentation enables the system to accommodate lattice mismatch while maintaining device quality.
Solution Approach 2:
Different regions of the growth substrate are assigned different seed compositions tailored to local requirements. The patterned seed regions have varying In and Al content to locally optimize the lattice parameter match with the overlying InxAlyGa1-x-yN layer. This local quality approach allows each region to minimize strain and defects according to its specific compositional needs, while the overall structure maintains high device quality.
2Adaptability or versatility
If multiple InGaN active regions with different InN content are grown on GaN, then multi-color emission is achieved, but material quality deteriorates when forced to lock to a single in-plane a-lattice parameter
Solution Approach 1:
The patent changes the compositional parameters of the underlying seed regions to enable different InxAlyGa1-x-yN active regions to have different in-plane a-lattice parameters. By varying the In and Al content in the patterned seed regions, each active region can be grown with its optimal lattice parameter, allowing multi-color emission without compromising material quality. This parameter change enables independent optimization of each emitter's performance.
3Object-affected harmful factors
If graded-layer approaches are used to grow relaxed InGaN, then lattice mismatch is reduced, but material quality deteriorates due to high densities of point defects
Solution Approach 1:
The patent performs preliminary action by pre-patterned seed regions with optimized compositions before growing the InxAlyGa1-x-yN layer. Instead of using graded layers to gradually transition compositions, the patterned seeds are prepared in advance with the exact compositions needed to match the desired InxAlyGa1-x-yN regions. This preliminary action eliminates the need for graded transitions, avoiding the generation of point defects while still reducing lattice mismatch.
4Reliability
If thick InGaN layers are grown to reduce crystalline defects, then defect density is reduced, but the approach is limited in achievable InN mole fractions and applicability
Solution Approach 1:
The patent applies local quality by using patterned seed regions with different compositions in different spatial locations. This allows thick InxAlyGa1-x-yN layers to be grown with high crystalline quality in each local region, while the overall structure can accommodate a wide range of InN mole fractions by varying the seed composition. Each region can be optimized for its specific InN content, achieving both low defect density and high adaptability.
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 enables the fabrication of high-quality, relaxed InGaN layers with reduced defect densities and increased lattice dilation, improving the performance and manufacturing feasibility of multi-color optoelectronic devices like LEDs and LDs.
Implementation Method 1
InxAlyGa1-x-yN grown on the patterned seed regions relaxes and subsequently coalesces to provide substantially relaxed (0001) InxAlyGa1-x-yN growth regions
Data Source
AI summary
InxAlyGa1-x-yN semiconductor structures having optoelectronic elements characterized by epitaxial layers having different in-plane a-lattice parameters and different InN mole fractions are disclosed. The active regions are configured to emit radiation in different wavelength ranges and are characterized by strain states within about 1% to 2% of compressive strain. The epitaxial layers are grown on patterned InxAlyGa1-x-yN seed regions on a single substrate, where the relaxed InGaN growth layers provide (0001) InxAlyGa1-x-yN growth surfaces characterized by different in-plane a-lattice parameters and different InN mole fractions. InxAlyGa1-x-yN semiconductor structures can be used in optoelectronic devices such as in light sources for illumination and in display applications.