LED Electrode Inclined Surface Light Extraction
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Solution Overview
Problem
Conventional light emitting devices face challenges in achieving high light extraction efficiency and uniform light emission due to absorption of light by lateral surfaces of electrodes, leading to reduced performance.
Innovation Solution
A light emitting device structure is developed with a reflective member on the lateral surface of the second electrode, which has an inclined and uneven surface, and a passivation layer extending from the channel layer to the lateral surface, enhancing light extraction efficiency and uniformity by minimizing light absorption and promoting even light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional planar electrode structure is used, then the device structure is simple, but light extraction efficiency is reduced due to light absorption by lateral electrode surfaces
Solution Approach 1:
The electrode lateral surface is transformed from a planar symmetric structure to an asymmetric structure with inclined surfaces and uneven topography. This asymmetric design redirects light that would otherwise be absorbed by the lateral surface, directing it toward extraction paths and improving overall light extraction efficiency.
Solution Approach 2:
The electrode surface is modified by adding dimensional complexity through inclined surfaces and uneven features. This transitions the surface from a 2D planar structure to a 3D structured surface, creating additional light extraction pathways and reducing light absorption by redirecting photons away from the electrode bulk.
2Loss of energy
If a reflective member is added on the lateral surface of the electrode, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The reflective member is integrated directly with the electrode structure, merging the electrical conduction function and the optical reflection function into a single hybrid component. This eliminates the need for separate reflective layers or additional structural elements, thereby improving light extraction efficiency without proportionally increasing device complexity.
Solution Approach 2:
The electrode structure is designed to perform multiple functions simultaneously: electrical conduction and optical reflection. By endowing the electrode with reflective properties through its structured lateral surface and integrated reflective member, the same component serves dual purposes, reducing the need for additional dedicated reflective elements.
3Loss of energy
If light is reflected away from electrode surfaces, then light extraction efficiency is improved, but light uniformity may be affected
Solution Approach 1:
The reflective properties and surface geometry are optimized locally at different regions of the electrode lateral surface. By varying the inclination angles, surface roughness, and reflective member distribution across different locations, the design achieves both efficient light extraction and uniform light emission by tailoring local optical characteristics to compensate for position-dependent variations.
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 solution significantly improves light extraction efficiency and achieves uniform light emission by reflecting light away from the electrode surfaces and ensuring consistent light distribution, thereby enhancing the overall performance of the light emitting device.
Implementation Method 1
a reflective member on the lateral surface of the second electrode... reflecting light away from the electrode surfaces
Data Source
Figure 1
Figure 2
Figure 3(a)~3(c)
AI summary
Provided is a light emitting device, which includes a metal layer (175), a light emitting structure (135) comprising a first conductive type semiconductor layer (130), an active layer (120), and a second conductive type semiconductor layer (110); an electrode (115) disposed on a first upper portion of the second conductive type semiconductor layer; a current spreading portion (116b) disposed on a second upper portion of the second conductive type semiconductor layer; an adhesive layer (170) disposed under the first conductive type semiconductor layer; an insulating layer (145) disposed between the electrode and the adhesive layer; and a passivation layer (180) disposed on an inclined surface of the light emitting structure and on a at least one upper surface of the light emitting structure, wherein the electrode (115) has a first layer, wherein the electrode contacts the current spreading portion (116b) and an upper surface of the electrode (115) has a first roughness, wherein an upper surface of the second conductive type semiconductor layer (110) has a second roughness, and wherein the current spreading portion (116b) has an inclined surface.