Nitride Semiconductor Light Emitting Device Stress Accommodation
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Solution Overview
Problem
Nitride-based light emitting devices face challenges in achieving high light emission efficiency and reliability due to strain and crystal defects caused by lattice mismatch in quantum well structures, leading to degraded performance and efficiency.
Innovation Solution
Incorporation of a stress accommodating layer, such as a super-lattice layer with alternating layers of different lattice constants, to mitigate stress and enhance the crystallinity of quantum well layers, thereby improving the confinement of electrons and holes and reducing defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitride semiconductor multi-quantum well structure is used to emit light, then light emission function is achieved, but strain and crystal defects are generated due to lattice mismatch between different material layers
Solution Approach 1:
A composition gradient layer is introduced as an intermediary between the quantum well layer and the barrier layer. This gradient layer has a composition that transitions gradually from the quantum well material to the barrier material, acting as a buffer that reduces the abrupt lattice mismatch. The gradient layer mediates the strain between different material layers, preventing dislocation generation and improving crystal quality while maintaining the light emission function of the quantum well structure.
Solution Approach 2:
The composition of the semiconductor layer is changed gradually through the composition gradient layer, transitioning from the quantum well composition to the barrier composition. This parameter change approach allows the lattice constant to vary continuously, reducing the abrupt mismatch that causes strain and defects. The gradual composition change maintains structural integrity while enabling the quantum well to function effectively for light emission.
2Reliability
If alternating layers of different materials are deposited to form quantum well structure, then electron and hole confinement is achieved, but stress is applied to quantum well layers due to material difference
Solution Approach 1:
The composition gradient layer serves as a stress-mediated transition zone between the quantum well layer and the barrier layer. By providing a gradual composition transition, this intermediary layer reduces the abrupt stress concentration that would otherwise be applied to the quantum well layer. The gradient layer absorbs and distributes the mechanical stress, preventing strain accumulation and maintaining quantum well layer stability.
3Ease of manufacture
If GaN-based semiconductor layers are grown on non-GaN substrates to enable device fabrication, then device manufacturing is enabled, but a large amount of defects are generated due to substrate mismatch
Solution Approach 1:
The composition parameter of the semiconductor layer is changed gradually through the composition gradient layer, transitioning from the quantum well composition to the barrier composition. This gradual parameter change reduces the abrupt lattice mismatch between layers grown on non-GaN substrates, minimizing defect generation while maintaining the ability to fabricate functional devices. The gradient layer acts as a buffer that accommodates substrate-induced strain.
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 stress accommodating layer effectively reduces compressive stress, enhances light emission efficiency, and improves the internal quantum efficiency of the nitride-based light emitting devices by uniformly distributing stress and optimizing the indium distribution within the quantum well layers.
Implementation Method 1
the stress accommodating layer, which contributes to a reduction in compressive stress applied to each quantum well layer
Implementation Method 2
electrons and holes respectively injected from an n-type semiconductor layer and a p-type semiconductor layer are coupled in the quantum well layers, thereby emitting light
Implementation Method 3
Light emitting diodes (LEDs) are well known as a semiconductor light emitting device which converts current to light, to emit light
Data Source
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AI summary
A nitride-based light emitting device capable of achieving an enhancement in light emission efficiency and an enhancement in reliability is disclosed. The nitride-based light emitting device includes a light emitting layer including a quantum well layer and a quantum barrier layer, and a stress accommodating layer arranged on at least one surface of the quantum well layer of the light emitting layer.