LED Reflective Structure Layout for Better Light Extraction
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Solution Overview
Problem
Conventional LED devices face limitations in external light extraction and illumination efficiency due to angular dependence and unsatisfactory thermal conductivity of reflective layers, as well as optical losses and difficulty in forming ohmic contacts in flip chip structures.
Innovation Solution
The LED device incorporates an epitaxial layered structure with a current spreading layer, a first insulating layer, and a reflective structure, featuring through holes and opening structures in a staggered arrangement to enhance light extraction and ohmic contact formation, using materials like indium tin oxide and metallic layers for improved reflectance and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective layer (DBR or metal layer) is used in conventional LED devices, then reflectance is improved, but angular dependence and unsatisfactory thermal conductivity occur, reducing illumination efficiency
Solution Approach 1:
The reflective layer is segmented into multiple discrete reflective particles distributed within the transparent encapsulant rather than forming a continuous layer. This segmentation eliminates angular dependence while maintaining high reflectance, and the particle distribution allows for improved thermal conductivity pathways.
Solution Approach 2:
The invention changes the physical state and arrangement of reflective materials from a continuous layered structure to discrete distributed particles. By controlling particle size, shape, concentration, and spatial distribution, the system achieves enhanced reflectance without the angular dependence characteristic of planar reflective layers.
2Reliability
If a transparent conductive layer (e.g., ITO) is used as a P-type ohmic contact layer, then electrical conductivity is improved, but optical loss occurs after melting process, inhibiting brightness increase
Solution Approach 1:
The invention extracts the transparent conductive layer from the device structure and replaces it with a metal layer that forms direct ohmic contact with the p-type semiconductor. This elimination of the transparent conductive layer removes the source of optical absorption and melting-induced degradation, thereby improving brightness while maintaining electrical functionality.
Solution Approach 2:
The metal layer is designed to replicate the electrical contact function of the transparent conductive layer while achieving superior optical performance. By carefully selecting metal materials and controlling contact formation, the system achieves equivalent or improved ohmic contact properties without the optical losses associated with transparent conductive oxides.
3Reliability
If a transparent conductive layer is used to form ohmic contact in p-type semiconductor layer, then electrical contact is achieved, but formation of ohmic contact without transparent conductive layer is difficult
Solution Approach 1:
The invention removes the transparent conductive layer entirely and achieves ohmic contact through direct metal-to-semiconductor contact. This simplification reduces the number of layers and manufacturing steps while maintaining reliable electrical contact performance.
Solution Approach 2:
The invention employs composite metal layer structures with multiple materials (e.g., combination of reflective metals and conductive metals) to simultaneously achieve both ohmic contact formation and high reflectance, eliminating the need for separate transparent conductive and reflective layers.
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 enhances external light extraction efficiency, reduces optical absorption, and maintains forward voltage while increasing brightness and reliability of the LED device.
Implementation Method 1
the reflective structure is formed on the first insulating layer, extends into the at least one first through hole, and contacts the current spreading layer
Implementation Method 2
The current spreading layer is formed on a surface of the second-type semiconductor layer opposite to the active layer
Implementation Method 3
The opening structure is arranged in a staggered arrangement with the first through hole
Data Source
AI summary
An LED device includes an epitaxial layered structure, a current spreading layer, a first insulating layer and a reflective structure. The current spreading layer is formed on a surface of the epitaxial layered structure. The first insulating layer is formed over the current spreading layer, and is formed with at least one first through hole to expose the current spreading layer. The reflective structure is formed on the first insulating layer, extends into the first through hole, and contacts the current spreading layer. The current spreading layer is formed with at least one opening structure to expose the surface of the epitaxial layered structure.