LED Attachment Layer Using Transition Metal Oxide for Light Transmission

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Solution Overview

Problem

Light emitting diodes (LEDs) with GaN p-n junctions suffer from low photon yield due to inefficient light reflection and transmission caused by the use of Indium Tin Oxide (ITO) as the attachment layer between the p-type GaN layer and the metal electrode.

Innovation Solution

Employing a transition metal oxide (TMO) such as molybdenum oxide (MoO3) as the attachment layer, which improves light reflection and transmission, reducing contact resistance, and maintaining high reflectance and transmission efficiency even at varying thicknesses, replacing ITO with TMO and silver metal electrode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If ITO is used as the attachment layer, then electrical connection is achieved, but light transmission and reflection efficiency is poor

Engineering Contradiction:

Improvelight transmission efficiencyVSAvoidelectrical connection

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The attachment layer is segmented into multiple functional layers: a TMO layer (MoO3, WO3, etc.) for light transmission and a metal layer (Ag, Al, Au, etc.) for electrical connection and light reflection. This segmentation allows each layer to specialize in one function, resolving the contradiction between light transmission efficiency and electrical connection reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The attachment layer uses composite materials combining TMO (transition metal oxide) and metal. The TMO provides high light transmission and reflection efficiency, while the metal provides excellent electrical conductivity and reflection. This composite structure simultaneously achieves both light transmission efficiency and electrical connection reliability.

Inventive Principle:

Principle #40Composite materials

2Productivity

If ITO is used as the attachment layer, then manufacturing process is established, but photon yield is low

Engineering Contradiction:

Improvephoton yieldVSAvoidmanufacturing process

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The invention changes the material parameters of the attachment layer by replacing ITO with TMO compounds (MoO3, WO3, V2O5, etc.). These TMO materials have different optical parameters with higher light transmission and reflection efficiency, directly improving photon yield while maintaining compatibility with existing manufacturing processes.

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If metal electrode layer is added for reflection, then light reflection is improved, but contact resistance increases

Engineering Contradiction:

Improvelight reflectionVSAvoidcontact resistance

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The attachment layer is segmented into multiple functional layers: a TMO layer (MoO3, WO3, V2O5, etc.) for light transmission and a metal layer (Ag, Al, Au, etc.) for electrical connection and light reflection. This segmentation allows each layer to specialize in one function, resolving the contradiction between light transmission efficiency and electrical connection reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

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

Significantly enhances the photon yield of LEDs by maintaining high light reflection and transmission efficiency, with molybdenum oxide achieving 94% reflection and over 80% transmission at 455 nm, compared to ITO's 75%, while reducing contact resistance and simplifying manufacturing with more readily available materials.

Implementation Method 1

the attachment layer comprises transition metal oxide and is configured to transmit light emitted by the p-n junction

Methodology Applied

Scientific EffectLight transmission: Light

Implementation Method 2

the first metal electrode layer configured to reflect light emitted by the p-n junction towards a light emitting side of the LED

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 3

the attachment layer comprises transition metal oxide and is configured to transmit light reflected by the metal electrode layer

Methodology Applied

Scientific EffectLight transmission: Light

Data Source

PatentUS8987749B2Light emitting diode and method for fabricating the same

Publication Date: 2015.03.24 INTERUNIVERSITAIR MICRO ELECTRONICS CENT (IMEC VZW)

AI summary

The disclosed technology relates to a light-emitting diode (LED) and a method of fabricating the same. In one aspect, the LED includes a GaN p-n junction formed at a junction between a p-type GaN layer and an n-type GaN layer. The LED further includes a first metal electrode layer provided on the p-type GaN layer, where the first metal electrode layer is configured to reflect light emitted by the p-n junction towards a light emitting side of the LED. The LED additionally includes an attachment layer interposed between and configured to electrically connect the p-type GaN layer and the metal electrode layer, wherein the attachment layer comprises a transition metal oxide and is configured to transmit light emitted by the p-n junction and to transmit light reflected by the metal electrode layer.