LED Reflecting Layer Refractive Index Design

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Solution Overview

Problem

Light emitting devices, particularly LEDs, face challenges in achieving high light extraction efficiency and preventing electrode peeling-off and separation, especially in flip-chip types designed for heat dissipation.

Innovation Solution

A light emitting device structure is developed with a first and second semiconductor layer, an active layer, and reflection layers with different refractive indices to enhance light emission and heat dissipation, including a first reflection layer on the second semiconductor layer and a second reflection layer overlapping the second electrode, along with an impact buffering layer for thermal conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a reflection layer is added to enhance light extraction efficiency, then light emission efficiency is improved, but device structure becomes more complex

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoiddevice structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The reflection layer is divided into multiple sub-layers with different refractive indices (first reflection layer with lower refractive index, second reflection layer with higher refractive index), allowing each layer to contribute differently to light extraction while managing overall structural complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The reflection layers are positioned specifically at the second semiconductor layer interface where light extraction is most needed, rather than uniformly throughout the device, optimizing light extraction efficiency at critical locations

Inventive Principle:

Principle #3Local quality

2Reliability

If electrode size is increased to improve electrical connection, then electrical conductivity is improved, but electrode peeling-off and separation occur

Engineering Contradiction:

Improveelectrical connectionVSAvoidelectrode separation

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The inclined surface is formed on the electrode before final assembly, creating a mechanical interlock structure in advance that prevents peeling-off during operation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The electrode side surface is designed with an inclined surface rather than a vertical flat surface, creating a tapered structure that mechanically resists peeling forces and improves bonding stability

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Temperature

If flip-chip type structure is used for heat dissipation, then heat dissipation efficiency is improved, but electrode separation risk increases

Engineering Contradiction:

Improveheat dissipation efficiencyVSAvoidelectrode separation

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The inclined surface structure is prepared in advance on the electrode before flip-chip assembly, providing mechanical reinforcement that counteracts the thermal stress and peeling risks introduced by the flip-chip configuration

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The electrode structure combines multiple materials or layers (conductive material with inclined surface configuration) to simultaneously achieve good electrical conductivity and enhanced mechanical bonding resistance to peeling

Inventive Principle:

Principle #40Composite materials

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 prevents electrode separation, enabling efficient heat dissipation and prolonged device lifespan while maintaining high brightness.

Implementation Method 1

a first reflection layer disposed on the second semiconductor layer, the first reflection layer being in contact with a side surface of the second electrode and a portion of an upper surface of the second electrode

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

the first reflection layer comprises at least a first layer having a first index of refraction, and a second layer disposed on the first layer and the second layer having a second index of refraction different from the first index of refraction

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

an impact buffering layer is additionally formed on an outer surface of the first reflection layer

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP2448019B1Reflecting layer for a light emitting diode

Publication Date: 2018.10.17 LG INNOTEK CO LTD

Figure 1
Figure 2(a)~2(b)
Figure 3

AI summary

A light emitting device is disclosed. The disclosed light emitting device includes a light emitting structure including a first semiconductor layer, a second semiconductor layer, and an active layer interposed between the first and second semiconductor layers, a first electrode electrically connected to the first semiconductor layer, a second electrode electrically connected to the second semiconductor layer, and a first reflection layer disposed on the second semiconductor layer. The first reflection layer includes at least a first layer having a first index of refraction and a second layer having a second index of refraction different from the first index of refraction. The first reflection layer is further disposed on a side surface of the second electrode and a portion of an upper surface of the second electrode.