Nitride Semiconductor Light-Emitting Device Protrusions
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Solution Overview
Problem
Nitride semiconductor light-emitting devices face challenges in light extraction efficiency due to the high refractive index of the semiconductor material, leading to total reflection and re-absorption of photons, and increased manufacturing complexity and cost from existing methods, as well as high dislocation density caused by lattice constant differences between substrates and semiconductor layers.
Innovation Solution
The solution involves forming protrusions on the substrate with recesses to increase the surface area for semiconductor growth, using a sapphire substrate with lattice-matched nitride semiconductor material, and etching techniques to create specific shapes and depths of protrusions that enhance light extraction and reduce dislocation density, thereby improving light extraction efficiency and internal quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat substrate is used for growing nitride semiconductor layers, then the manufacturing process is simple, but the light extraction efficiency is low due to total internal reflection
Solution Approach 1:
The patent forms protrusions with curved surfaces on the substrate before growing nitride semiconductor layers. The curved surfaces have different orientations than flat substrates, allowing light to escape at angles that avoid total internal reflection. This curvature-based approach improves light extraction efficiency while maintaining manufacturing simplicity, as the protrusions are formed in a single epitaxial growth process rather than requiring separate fabrication steps.
2Loss of energy
If a stacking-structure wall with predetermined angle is formed to extract transverse light, then light extraction efficiency improves, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of forming complex stacking structures with predetermined angles through multiple fabrication steps, the patent uses protrusions with curved surfaces formed directly during epitaxial growth. The curved geometry naturally provides multiple light extraction paths without requiring precise angular control or additional processing steps, thereby improving light extraction while avoiding increased manufacturing complexity.
Solution Approach 2:
The patent changes the surface geometry parameter from flat to curved protrusions, and controls the curvature radius and height of protrusions to optimize light extraction. By adjusting these geometric parameters during a single growth process, the patent achieves improved light extraction efficiency without introducing complex manufacturing steps or increasing device structure complexity.
3Ease of manufacture
If nitride semiconductor layers are grown on standard substrates, then the manufacturing process is straightforward, but dislocation density increases due to lattice constant mismatch
Solution Approach 1:
The patent segments the growth surface into multiple protrusions with curved surfaces, each having different local orientations. This segmentation allows the nitride semiconductor layers to grow on surfaces with orientations that better match the crystal structure, reducing lattice mismatch and dislocation density. The segmented approach maintains manufacturing simplicity by forming all protrusions in a single growth process without requiring substrate pre-processing.
Solution Approach 2:
The patent changes the surface orientation parameter by forming protrusions with specific curvature radii and heights, which create local growth surfaces with orientations that reduce lattice mismatch. By controlling these geometric parameters, the patent achieves lower dislocation density while maintaining a straightforward manufacturing process that forms protrusions during epitaxial growth without additional steps.
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 significantly improves light extraction efficiency by 40% and internal quantum efficiency by 10%, while reducing dislocation density and manufacturing complexity, resulting in a more efficient and cost-effective nitride semiconductor light-emitting device.
Implementation Method 1
forming one or more first protrusions on the substrate, each first protrusion having a recess through which a surface of the substrate is exposed planarly
Implementation Method 2
forming one or more first protrusions on the substrate, each first protrusion having a recess through which a surface of the substrate is exposed planarly
Implementation Method 3
using a sapphire substrate with lattice-matched nitride semiconductor material
Data Source
AI summary
A semiconductor light-emitting device and a method for manufacturing the same is disclosed, which improves light extraction efficiency by forming a plurality of protrusions on a surface of a substrate for growing a nitride semiconductor material thereon, the semiconductor light-emitting device comprising a substrate; one or more first protrusions on the substrate, each first protrusion having a recess through which a surface of the substrate is exposed planarly; a first semiconductor layer on the substrate including the first protrusions; an active layer on the first semiconductor layer; a second semiconductor layer on the active layer; a first electrode on a predetermined portion of the first semiconductor layer, wherein the active layer and second semiconductor layer are not formed on the predetermined portion of the first semiconductor layer; and a second electrode on the second semiconductor layer.