LED Electrode Segmentation for Voltage and Light Extraction
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Solution Overview
Problem
Lateral-type light emitting devices face issues with reliability due to increased operating voltage and degraded light extraction efficiency caused by light absorption of the electrode layer, as well as significant losses during mesa etching.
Innovation Solution
The light emitting device incorporates a substrate with a predetermined concave-convex structure, an insulating layer between the ohmic and pad electrodes, and a branch electrode structure that includes both ohmic and reflective materials to reduce voltage and enhance light extraction, while maintaining a wider active layer to improve carrier injection and light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If mesa etching is performed with respect to a wide area to ensure a wider active layer, then the active layer area is increased, but significant loss occurs at the active layer
Solution Approach 1:
The electrode layer is divided into multiple segments (first electrode layer and second electrode layer) that are spatially separated and selectively positioned. The first electrode layer contacts the first conductive type semiconductor layer while the second electrode layer contacts the second conductive type semiconductor layer, avoiding direct contact with the active layer and thus reducing losses while maintaining wide area coverage.
2Reliability
If the electrode layer is used for electrical connection with the nitride semiconductor layer, then electrical connection is achieved, but operating voltage increases and reliability decreases
Solution Approach 1:
An insulating layer is introduced as an intermediary between the electrode layer and the semiconductor layers. The insulating layer is selectively removed at contact regions to enable electrical connection, while maintaining insulation in other areas. This controlled intermediary approach ensures reliable electrical connection at intended points while preventing unwanted conduction paths that would increase operating voltage and reduce reliability.
3Reliability
If the electrode layer is present in the light path, then electrical connection is provided, but light extraction efficiency is degraded due to light absorption
Solution Approach 1:
The electrode structure is segmented into multiple layers with different functions. The first electrode layer provides electrical connection while the second electrode layer is positioned to reflect light. The insulating layer segments the electrical connection paths, allowing the electrode to perform electrical function without blocking the light path, thus maintaining both electrical connection and light extraction efficiency.
Solution Approach 2:
Different regions of the electrode structure are assigned different properties. The first electrode layer has high electrical conductivity for connection, while the second electrode layer has high reflectivity for light extraction. The insulating layer provides electrical insulation in regions where light extraction is critical. This local differentiation allows each component to optimize its specific function without compromising the other.
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 increases light intensity and wall-plug efficiency, improving the reliability and light extraction efficiency of the device by reducing operating voltage and minimizing light absorption, as demonstrated in various embodiments.
Implementation Method 1
a light emitting device (LED) includes a p-n junction diode having a characteristic of converting electric energy into light energy
Implementation Method 2
a second electrode layer... having a reflective property
Data Source
Figure 1~2A
Figure 2B~3
Figure 4~5
AI summary
Disclosed are a light emitting device, a method of fabricating the same, a light emitting device package, and a lighting system. The light emitting device may include a substrate (105), a first conductive semiconductor layer (112) on the substrate, an active layer (114) on the first conductive semiconductor layer, a second conductive semiconductor layer (116) on the active layer, an ohmic layer (120) on the second conductive semiconductor layer, an insulating layer (130) on the ohmic layer, a first branch electrode (140) electrically connected with the first conductive semiconductor layer, a first pad electrode (142) connected with the first branch electrode for electrical connection with the first conductive semiconductor layer, a second pad electrode (152) in contact with the ohmic layer through the insulating layer, a second branch electrode (150) connected with the second pad electrode on the insulating layer, and a second through electrode (154) passing through the insulating layer to connect the second branch electrode with the ohmic layer.