Nitride Semiconductor Layer Refractive Index Gradient for Light Extraction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current light emitting devices, particularly GaN-based LEDs, face limitations in achieving high light extraction efficiency despite optimizations in active layer design and patterned sapphire substrates.
Innovation Solution
A light emitting device structure is developed with a nitride semiconductor layer having a refractive index less than the second conductive semiconductor layer, where the refractive index is gradually reduced from the active layer to the second conductive semiconductor layer, enhancing light extraction efficiency by controlling the Al composition, and incorporating a transmissive ohmic layer and transparent insulating layer to facilitate carrier injection and light emission in the upward direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a patterned sapphire substrate and roughening are used to improve light extraction efficiency, then light extraction efficiency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the refractive index parameter of the semiconductor layer by adjusting the Al composition ratio in the nitride semiconductor layer. This parameter change enables light extraction efficiency improvement through optical property modification rather than complex structural modifications, thereby resolving the contradiction between ease of manufacture and device complexity
Solution Approach 2:
The patent employs a composite nitride semiconductor layer structure with varying Al composition ratios (e.g., AlGaN layers with different x values) to create a gradient refractive index structure. This composite material approach achieves enhanced light extraction through material composition gradients rather than complex geometric patterns, reducing manufacturing complexity while maintaining effectiveness
2Ease of manufacture
If the Al composition ratio in the nitride semiconductor layer is increased to reduce refractive index, then light extraction efficiency improves, but material composition control difficulty increases
Solution Approach 1:
The patent systematically varies the Al composition ratio parameter (x in AlxGa1-xN) across different layers to achieve the desired refractive index gradient. By establishing specific composition ranges (e.g., 0.1≤x≤0.5 for certain layers), the patent balances optical performance improvement with manufacturable composition control, resolving the contradiction between ease of manufacture and manufacturing precision
Solution Approach 2:
The patent applies different Al composition ratios to different regions/layers of the semiconductor structure. Each layer has locally optimized composition (e.g., higher Al content near the active layer, lower Al content in upper layers) to create the refractive index gradient needed for light extraction, while maintaining overall compositional control within manufacturing capabilities
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 configuration significantly improves light extraction efficiency by directing light emission upward rather than laterally, increasing optical efficiency and enabling higher output in light emitting devices.
Implementation Method 1
a nitride semiconductor layer having a refractive index less than a refractive index of the second conductive semiconductor layer on the second conductive semiconductor layer
Implementation Method 2
light extraction efficiency
Data Source
AI summary
Disclosed are a light emitting device, a method of manufacturing the same, a light emitting device package, and a lighting system. The light emitting device includes: a substrate; a first conductive semiconductor layer on the substrate; an active layer on the first conductive semiconductor layer; a second conductive semiconductor layer; and a nitride semiconductor layer having a refractive index less than a refractive index of the second conductive semiconductor layer on the second conductive semiconductor layer.