Three-Layer Reflective LED Structure for Higher Light Extraction
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Solution Overview
Problem
Existing light-emitting elements face challenges in achieving higher output power and reliability.
Innovation Solution
A light-emitting element design that includes a semiconductor layered structure with a reflective portion comprising multiple layers, an insulative layer, a light-transmissive conductive layer, and electrodes to enhance light extraction efficiency and reduce light absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single reflective layer is used between the electrode and semiconductor layer, then the structure is simple, but light extraction efficiency is insufficient
Solution Approach 1:
The reflective portion is divided into three distinct layers: a first reflective layer (e.g., TiN or ITO) for initial light reflection, a second reflective layer (e.g., Al or Ag) for enhanced reflection, and a third insulative layer (e.g., SiO2 or Si3N4) for protection and electrical isolation. This segmentation allows each layer to perform its specific function optimally, achieving high light extraction efficiency while maintaining structural organization.
Solution Approach 2:
The reflective portion uses a composite structure combining different materials with complementary properties: conductive transparent materials (TiN, ITO) for electrical and optical functionality, highly reflective metals (Al, Ag) for maximum light reflection, and insulative materials (SiO2, Si3N4) for protection. This composite approach resolves the contradiction by integrating multiple material advantages into a unified structure that simultaneously improves light extraction while managing complexity through functional specialization.
2Power
If the electrode directly contacts the semiconductor layer, then the manufacturing process is simple, but light absorption by the electrode reduces output power
Solution Approach 1:
A light-transmissive conductive layer (e.g., ITO or TiN) is introduced as an intermediary between the electrode and the semiconductor layer. This intermediate layer serves dual functions: it maintains electrical connection while allowing light to pass through to the reflective portion, and it prevents direct contact between the electrode and semiconductor, reducing light absorption and improving output power.
3Reliability
If no insulative layer is provided over the reflective portion, then the structure is simpler, but reliability is reduced due to potential damage and contamination
Solution Approach 1:
A third insulative layer (e.g., SiO2 or Si3N4) is provided over the second reflective layer as a protective cushion before the device is subjected to operational stresses. This layer prevents damage to the underlying reflective layers, blocks contamination from the external environment, and provides electrical isolation, thereby enhancing reliability before issues can occur.
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 proposed design achieves higher output power and reliability by effectively reflecting light and reducing absorption, thereby improving light extraction efficiency.
Implementation Method 1
a second layer made of a metal material provided on the first layer
Data Source
AI summary
A light-emitting element includes: a semiconductor layered structure including a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type, and an active layer located between the first semiconductor layer and the second semiconductor layer; a reflective portion including an insulative first layer located on the first semiconductor layer, a second layer made of a metal material located on the first layer, and a third layer located on the second layer; an insulative layer covering the reflective portion; a light-transmissive conductive layer located on the insulative layer and on the first semiconductor layer; a first electrode located on a portion of the light-transmissive conductive layer that is above the reflective portion; and a second electrode located on the second semiconductor layer.