Group III Nitride LED Groove Pattern for Light Extraction
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Solution Overview
Problem
Conventional methods for enhancing light-out efficiency in group III nitride semiconductor light-emitting devices, such as the laser lift-off process and two-step concavo-convex processing, result in uneven surfaces and increased driving voltage due to the formation of thin and thick portions in the n-type layer.
Innovation Solution
A method involving the formation of grooves in the n-type layer with a depth reaching the p-type layer, covered by a light-transmitting insulating film, and a wiring-shaped n-electrode, which improves light-out efficiency without increasing driving voltage by ensuring a continuous surface and efficient current diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If two-step concavo-convex processing is performed to improve light taking-out efficiency, then light taking-out efficiency is improved, but driving voltage increases due to formation of thin and thick portions in the n-type layer
Solution Approach 1:
The invention divides the light extraction enhancement into two independent components: (1) grooves formed in the n-type layer to extract light from the bulk, and (2) fine unevenness formed only on the exposed flat surface for light extraction at the surface. This segmentation prevents the formation of thin and thick portions that would increase driving voltage, while still achieving enhanced light extraction through the grooves without compromising the uniformity of the n-type layer thickness in the current conduction path.
Solution Approach 2:
The invention applies different surface treatments to different regions: grooves are formed in specific patterns to enhance light extraction from the bulk, while fine unevenness is formed only on the exposed flat surface areas. This local differentiation allows optimized light extraction in each region without creating harmful thickness variations across the entire n-type layer, thus improving light efficiency without increasing driving voltage.
2Illumination intensity
If fine concavo-convex processing is performed by wet etching on the n-type layer surface, then light taking-out efficiency is enhanced, but uneven surfaces with flat and unevenness regions remain
Solution Approach 1:
The surface is segmented into two distinct regions: (1) groove regions where deep etching is performed to enhance light extraction, and (2) exposed flat surface regions where only fine unevenness is formed. This segmentation allows each region to have optimized surface characteristics for its specific function, achieving both light extraction enhancement and controlled surface uniformity where required.
Solution Approach 2:
The grooves are formed first as a preliminary action to create the main light extraction structures, followed by formation of fine unevenness only on the remaining flat surfaces. This sequential approach ensures that the fine unevenness is formed only where needed, avoiding the creation of unwanted thick portions and maintaining surface uniformity in the exposed regions.
3Illumination intensity
If grooves are formed in grid pattern to enhance light extraction, then light taking-out efficiency is improved, but the n-type layer is divided into thin and thick portions
Solution Approach 1:
The groove pattern is designed with specific characteristics (depth, width, spacing, and shape) to extract light efficiently while minimizing the impact on current distribution. The grooves are configured to remove light without creating significant thin portions that would affect electrical properties, and the spaces between grooves maintain sufficient n-type layer thickness for uniform current flow.
Solution Approach 2:
The groove parameters (depth, width, spacing, shape) are optimized to achieve the right balance between light extraction efficiency and electrical performance. By carefully controlling these parameters, the grooves can extract light effectively while maintaining sufficient n-type layer thickness in the regions between grooves to ensure uniform current distribution and prevent excessive voltage increase.
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 described method enhances light-out efficiency by up to 15% while maintaining the same driving voltage as comparative examples, with grooves arranged in patterns that prevent surface division and promote even current diffusion.
Implementation Method 1
irradiating an interface between the growth substrate and the group III nitride semiconductor with a laser beam to decompose the group III nitride semiconductor layer
Implementation Method 2
dissolving the above-mentioned chemical solution soluble layer with a desired chemical solution, thereby removing the growth substrate
Data Source
AI summary
A group III nitride semiconductor light-emitting device includes: a conductive support; a p-electrode positioned on the support, a p-type layer containing a group III nitride semiconductor, an active layer and an n-type layer having a first surface, which are positioned in turn on the p-electrode; and an n-electrode positioned on the first surface of the n-type layer. A groove is formed in the first surface of the n-type layer in a pattern such that the first surface of the n-type layer is continuous. A light-transmitting insulating film is formed on side surface and bottom surface of the groove. The groove has a depth at least reaching the p-type layer. The n-electrode is formed in wiring form.