Nitride LED Stress Relief Structure for Lattice Defect Control
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Solution Overview
Problem
Existing light-emitting diodes (LEDs) face challenges in achieving high luminous efficiency due to lattice mismatch and defects in the active structure, leading to reduced radiative recombination of electrons and holes.
Innovation Solution
A light-emitting device with a nitride semiconductor structure that includes a stress relief structure composed of alternately stacked narrow and wide band gap layers, an active structure with quantum well and barrier layers, and an electron blocking structure, designed to enhance the radiative recombination efficiency by adjusting band gaps and reducing lattice defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the active structure is grown directly on the substrate without stress relief structure, then the device complexity is reduced, but lattice mismatch and defects occur leading to reduced radiative recombination efficiency
Solution Approach 1:
A stress relief structure comprising alternating narrow band gap and wide band gap layers is grown before the active structure to pre-relax the epitaxial lattice and reduce dislocation density. This preliminary action prevents lattice mismatch from propagating into the active region, thereby improving radiative recombination efficiency without requiring complex post-growth processing.
Solution Approach 2:
The stress relief structure acts as an intermediary layer between the substrate and the active structure. The alternating narrow and wide band gap layers serve as a transition zone that gradually accommodates the lattice mismatch, reducing defects that would otherwise directly affect the active region's radiative recombination efficiency.
2Reliability
If the aluminum composition in wide band gap layer is increased to improve carrier blocking, then the band gap increases improving electron blocking, but the lattice mismatch with underlying layers increases
Solution Approach 1:
The electron blocking capability is enhanced by locally increasing the aluminum composition in the wide band gap layer of the stress relief structure, creating a higher potential barrier for electrons. This local quality adjustment allows effective electron blocking at the specific interface region without requiring uniform high aluminum content throughout the entire structure, thereby limiting the propagation of lattice mismatch.
Solution Approach 2:
The aluminum composition in the wide band gap layer is optimized to balance two competing requirements: sufficient aluminum content to create an effective electron blocking barrier, and controlled aluminum content to limit lattice mismatch with underlying layers. This parameter optimization achieves the desired electron blocking capability while maintaining acceptable lattice matching precision.
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 proposed structure improves the radiative recombination efficiency of electrons and holes, enhancing the luminous efficiency of the LED by smoothly relaxing the epitaxial lattice and optimizing the distribution of charge carriers.
Implementation Method 1
a stress relief structure on the first nitride semiconductor structure comprising narrow band gap layers and wide band gap layers alternately stacked
Implementation Method 2
an active structure on the stress relief structure comprising quantum well layers and barrier layers alternately stacked, wherein one of the barrier layers comprises barrier sub-layers and one of the barrier sub-layers comprises aluminum
Implementation Method 3
an electron blocking structure on the active structure
Data Source
AI summary
A light-emitting device includes a first nitride semiconductor structure; a stress relief structure on the first nitride semiconductor structure including a plurality of narrow band gap layers and a plurality of wide band gap layers alternately stacked, wherein one of the plurality of wide band gap layers includes a plurality of wide band gap sub-layers and one of the plurality of wide band gap sub-layers includes aluminum; an active structure on the stress relief structure including a plurality of quantum well layers and a plurality of barrier layers alternately stacked, wherein one of the plurality of barrier layers includes a plurality of barrier sub-layers and one of the plurality of barrier sub-layers includes aluminum, an aluminum composition of the wide band gap sub-layer is greater than or equal to that of the barrier sub-layer, and an average aluminum composition of the wide band gap layer is greater than that of the barrier layer; and an electron blocking structure on the active structure.