Composite Substrate for III-Nitride Light Emitting Devices
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Solution Overview
Problem
III-nitride semiconductor light emitting devices face performance and reliability issues due to strain and crystal defects caused by growing on non-native substrates with different lattice constants, leading to suboptimal performance.
Innovation Solution
A composite substrate with III-nitride islands connected by a bonding layer is used, allowing the III-nitride semiconductor structures to be grown with reduced strain by having an a-lattice constant greater than 3.19 angstroms, which mitigates the lattice mismatch and crystal defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If III-nitride semiconductor structures are grown on non-native substrates (sapphire, SiC), then manufacturing cost is reduced and substrate availability is improved, but lattice mismatch causes strain and crystal defects that worsen device performance and reliability
Solution Approach 1:
The patent introduces a composite substrate as an intermediary structure between the non-native substrate and the III-nitride semiconductor structures. This composite substrate includes a native III-nitride layer that serves as a mediator, providing a lattice-matched foundation for growing high-quality III-nitride device structures while enabling the use of cost-effective non-native substrates like sapphire or SiC.
Solution Approach 2:
The patent employs a composite substrate structure consisting of multiple layers: a non-native substrate (sapphire or SiC), a bonding layer, and a native III-nitride layer. This composite structure combines the advantages of low-cost substrates with the lattice-matching benefits of native III-nitride material, resolving the contradiction between manufacturing ease and device reliability.
2Ease of manufacture
If III-nitride semiconductor structures are grown on non-native substrates, then manufacturing cost is reduced, but strain and crystal defects increase leading to worse device efficiency
Solution Approach 1:
The native III-nitride layer in the composite substrate acts as an intermediary that eliminates the harmful effect of lattice mismatch. This allows the use of inexpensive non-native substrates while maintaining the high crystalline quality and energy efficiency characteristic of native III-nitride growth, thus resolving the contradiction between manufacturing cost and device efficiency.
Solution Approach 2:
The substrate structure is segmented into distinct functional layers: the non-native substrate provides mechanical support and cost benefits, the bonding layer provides structural integrity, and the native III-nitride layer provides the crystalline foundation for efficient light emission. This segmentation allows each layer to optimize its function without compromising the others.
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 reduces strain in the light emitting layer, improving the performance and reliability of III-nitride semiconductor devices by allowing the light emitting layer to have a larger a-lattice constant, thus enhancing device efficiency.
Implementation Method 1
The composite substrate includes a plurality of islands of III-nitride material connected to a host by a bonding layer
Data Source
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AI summary
A plurality of III-nitride semiconductor structures, each comprising a light emitting layer disposed between an n-type region and a p-type region, are grown on a composite substrate. The composite substrate includes a plurality of islands of III-nitride material connected to a host by a bonding layer. The plurality of III-nitride semiconductor structures are grown on the III-nitride islands. The composite substrate may be formed such that each island of III-nitride material is at least partially relaxed. As a result, the light emitting layer of each semiconductor structure has an a-lattice constant greater than 3.19 angstroms.