GaN Pillar LED with Subwavelength TCL for Wide Viewing Angle
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Solution Overview
Problem
Gallium nitride-type light emitting diodes face restricted viewing angles due to refractive index differences at the semiconductor-air interface, limiting their light emission efficiency.
Innovation Solution
The use of a pillar structure with a transparent conductive layer having a subwavelength surface structure, where the pillar structures are formed with semiconductor layers and an electrical isolation layer, and the transparent conductive layer is contacted with the isolation layer to enhance light distribution and reduce leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional planar LED structure is used, then the manufacturing process is simple, but the viewing angle is restricted due to total internal reflection at the semiconductor-air interface
Solution Approach 1:
The LED structure is segmented into multiple vertical pillar structures arranged in an array on the substrate. Each pillar acts as an independent light-emitting unit, allowing light to be extracted from the sidewalls at multiple angles. This segmentation breaks the conventional planar structure and enables omnidirectional light emission, resolving the viewing angle restriction while maintaining manufacturing simplicity through standard semiconductor fabrication processes
Solution Approach 2:
The invention transitions from a two-dimensional planar LED structure to a three-dimensional array of vertical pillars. By adding the vertical dimension and utilizing sidewall light extraction, the design achieves omnidirectional emission patterns. The pillar height and spacing are optimized to maximize light extraction in all directions, transforming the light emission geometry from planar to volumetric
2Illumination intensity
If the viewing angle is increased using conventional packaging methods, then the light distribution is improved, but the device complexity increases with additional components
Solution Approach 1:
The LED structure itself is designed to provide omnidirectional light emission through its pillar geometry and optical properties. The sidewalls of the pillars naturally extract light at various angles without requiring external reflectors, lenses, or complex packaging components. The structure serves its own optical function, eliminating the need for additional light-manipulating components and simplifying the overall device
3Illumination intensity
If a transparent conductive layer with subwavelength surface structure is added to the pillar structure, then the viewing angle increases to over 160 degrees, but the manufacturing process becomes more complex
Solution Approach 1:
The transparent conductive layer is designed with subwavelength surface structures (such as nanoscale gratings or textured surfaces) that modify the optical parameters of the layer. These subwavelength features manipulate light propagation and enhance extraction efficiency at wide angles through diffraction and scattering effects. The layer thickness, pattern size, and material composition are optimized to achieve omnidirectional emission while maintaining electrical conductivity and transparency
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 localizes light within the pillar structure, increasing the viewing angle beyond conventional limits to over 160 degrees and reduces leakage current significantly.
Implementation Method 1
By means of the pillar structure, the light from the active layer can be localized in the pillar structure
Implementation Method 2
the refractive index difference at the interface between the semiconductor and the air may result in a total reflection phenomenon
Implementation Method 3
due to a transparent conductive layer having a subwavelength surface structure, the light exited from the transparent conductive layer has a large viewing angle
Implementation Method 4
Each of the pillar structures includes a first type semiconductor layer, an active layer, and a second type semiconductor layer
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~4C
AI summary
A light emitting diode includes a substrate, a plurality of pillar structures, a filler structure, a transparent conductive layer, a first electrode, and a second electrode. These pillar structures are formed on the substrate. Each of the pillar structures includes a first type semiconductor layer, an active layer, and a second type semiconductor layer. The first type semiconductor layers are formed on the substrate. The pillar structures are electrically connected with each other through the first type semiconductor layers. The filler structure is formed between the pillar structures. The filler structure and the second type semiconductor layers of the pillar structures are covered with the transparent conductive layer. The first electrode is in contact with the transparent conductive layer. The second electrode is in contact with the first type semiconductor layer.