Relaxed Strained Layer Composite Substrate for III-Nitride LEDs
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Solution Overview
Problem
Conventional semiconductor light-emitting devices face challenges in achieving efficient light emission due to strain-induced defects and rough surface morphology in III-nitride light emitting layers, particularly when grown on GaN buffer layers, which limits their efficiency and quality.
Innovation Solution
The introduction of a donor layer with a strained layer and a relaxed layer, along with a mule layer, allows for the relaxation of the epitaxial structure, thereby changing the in-plane lattice constant and reducing strain in the light emitting layer, which is grown on a seed layer formed from the relaxed donor layer, leading to improved light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a GaN buffer layer is used to grow III-nitride light emitting layers, then the device structure is simplified and manufacturing is easier, but strain-induced defects and rough surface morphology occur, reducing light emission efficiency
Solution Approach 1:
The patent introduces a composite substrate with a relaxed seed layer as an intermediary between the GaN buffer layer and the III-nitride light emitting layers. This relaxed seed layer acts as a mediator that accommodates lattice mismatch and reduces strain, preventing defect formation while maintaining the simplified GaN buffer layer structure. The composite substrate includes a host substrate, bonding layer, and relaxed seed layer that collectively serve this intermediary function.
Solution Approach 2:
The patent changes the lattice constant parameter of the seed layer by using a relaxed III-nitride material with a bulk lattice constant closer to the light emitting layer. This parameter change in the seed layer's in-plane lattice constant reduces the strain on subsequent layers, improving light emission efficiency without complicating the manufacturing process.
2Reliability
If a relaxed seed layer with bulk lattice constant closer to the light emitting layer is used, then strain is reduced and light emission efficiency improves, but the device structure becomes more complex
Solution Approach 1:
The patent segments the substrate structure into distinct functional layers: a host substrate for mechanical support, a bonding layer for attachment, and a relaxed seed layer for lattice matching. This segmentation allows each layer to be optimized independently and facilitates the transfer of the relaxed seed layer to different GaN buffer layers, managing complexity through modular design.
Solution Approach 2:
The patent resolves the complexity issue by separating the relaxation process from the growth process. The seed layer is relaxed on a host substrate in one dimension, then transferred to the light emitting structure in another dimension. This dimensional separation allows the relaxed seed layer to be reused across multiple devices, reducing overall device complexity.
3Manufacturing precision
If the seed layer is relaxed by disconnecting it from the growth substrate, then the in-plane lattice constant increases and matches the light emitting layer better, but additional processing steps are required
Solution Approach 1:
The patent performs the relaxation action preliminarily by growing the seed layer on a host substrate and allowing it to relax before transferring it to the final device structure. This preliminary relaxation ensures the seed layer achieves its bulk lattice constant early in the process, improving lattice constant matching without requiring complex in-situ relaxation techniques during device fabrication.
Solution Approach 2:
The host substrate and bonding layer serve as intermediaries that enable the relaxation process. The host substrate provides a platform for growing and relaxing the seed layer, while the bonding layer facilitates controlled detachment and transfer. These intermediary elements simplify the overall process by providing a dedicated relaxation zone separate from the final device 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 method results in a semiconductor light-emitting device with reduced strain and improved light emission efficiency, as the light emitting layer grown on the relaxed seed layer exhibits less strain and higher quality compared to conventional devices, enhancing the overall performance.
Implementation Method 1
The epitaxial structure is treated to cause the strained layer to relax. Relaxation of the strained layer causes an in-plane lattice constant of the donor layer to change.
Data Source
AI summary
A method according to embodiments of the invention includes providing an epitaxial structure comprising a donor layer and a strained layer. The epitaxial structure is treated to cause the strained layer to relax. Relaxation of the strained layer causes an in-plane lattice constant of the donor layer to change.