GaN LED Active Layers Extending into Pits to Reduce Dislocations
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Solution Overview
Problem
The fabrication of high-quality gallium nitride LEDs is hindered by crystal lattice mismatches between substrates and gallium nitride, leading to dislocation defects and reduced device efficiency, with existing methods either requiring shorting contacts or having unsatisfactory lattice matches with silicon carbide substrates.
Innovation Solution
The approach involves creating a pit opening region with expanded pit sizes to allow active layers to extend into the pits, using a pit opening layer that can be a superlattice structure or bulk GaN/AlGaN, and closing the pits with a contact layer, which enhances the device's radiant output and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum nitride buffer layer is used to overcome crystal lattice mismatch, then device reliability is improved, but device complexity increases due to required shorting contacts
Solution Approach 1:
The invention extracts and eliminates the shorting contact structure from the device architecture by using a conductive buffer layer that provides electrical connection through the buffer layer itself, rather than requiring separate bypass contacts
Solution Approach 2:
The conductive buffer layer performs multiple functions simultaneously: it provides crystal lattice matching to improve growth quality, maintains electrical conductivity to eliminate shorting contacts, and serves as the buffer between substrate and active layer
2Device complexity
If conductive buffer layer materials are used to eliminate shorting contacts, then device complexity is reduced, but manufacturing precision deteriorates due to unsatisfactory crystal lattice match with silicon carbide
Solution Approach 1:
The invention uses composite buffer layer structures combining different materials (such as AlN and GaN layers) to achieve both good crystal lattice matching with silicon carbide substrates and sufficient electrical conductivity to eliminate shorting contacts
3Manufacturing precision
If pits are closed before active region formation to improve device quality, then manufacturing precision is improved, but active layer performance is reduced by preventing active layers from extending into pits
Solution Approach 1:
The invention performs preliminary pit opening or modification actions before active region formation, creating optimized pit structures that allow subsequent active layers to extend into them, thereby improving both device quality and radiant output
4Productivity
If active layers are extended into open pits, then radiant output is increased, but device robustness may be compromised by exposing active regions to pit defects
Solution Approach 1:
The invention applies local quality modifications by creating specific pit opening regions with controlled characteristics, allowing active layers to extend into optimized pit structures while maintaining overall device robustness through localized rather than universal pit exposure
Data Source
AI summary
Light emitting devices include an active region comprising a plurality of layers and a pit opening region on which the active region is disposed. The pit opening region is configured to expand a size of openings of a plurality of pits to a size sufficient for the plurality of layers of the active region to extend into the pits. In some embodiments, the active region comprises a plurality of quantum wells. The pit opening region may comprise a superlattice structure. The pits may surround their corresponding dislocations and the plurality of layers may extend to the respective dislocations. At least one of the pits of the plurality of pits may originate in a layer disposed between the pit opening layer and a substrate on which the pit opening layer is provided. The active region may be a Group III nitride based active region. Methods of fabricating such devices are also provided.