LED Strain-Enhanced Well Layer for Efficiency Droop

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Solution Overview

Problem

High brightness LEDs experience a droop phenomenon where optical output efficiency decreases with increasing drive current, necessitating a solution to relieve strain and enhance efficiency.

Innovation Solution

Incorporating a strain-enhancing layer with a lower lattice constant than the barrier layer to apply compressive strain to the well layer, thereby reducing Auger recombination and maintaining high optical efficiency at high drive currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If drive current is increased to achieve high brightness, then light output increases, but optical efficiency decreases due to droop phenomenon

Engineering Contradiction:

Improvelight outputVSAvoidoptical efficiency

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The patent applies strain engineering by introducing a strain-enhancing layer with different lattice constant to modify the physical state of the well layer. This changes the energy band structure and carrier distribution parameters, reducing Auger recombination and mitigating the droop phenomenon, thereby maintaining high optical efficiency at high drive currents

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If strain is applied to the well layer to reduce droop, then optical efficiency improves, but device complexity increases due to additional layers

Engineering Contradiction:

Improveoptical efficiencyVSAvoidstructure complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The patent introduces a strain-enhancing layer as an intermediary component between the barrier layer and the well layer. This intermediate layer serves the specific function of applying compressive strain to the well layer through lattice mismatch, thereby improving optical efficiency without directly modifying the contact layers or substrate

Inventive Principle:

Principle #24Intermediary (Mediator)

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 strain-enhancing layer effectively reduces the droop phenomenon by increasing the energy level difference, leading to higher electro-luminescent intensity and external quantum efficiency even at high drive currents.

Implementation Method 1

a strain-enhancing layer configured to enhance a strain applied to the well layer

Methodology Applied

Scientific EffectStrain: Deformation

Implementation Method 2

the strain-enhancing layer comprising a lattice constant lower than a lattice constant of the barrier layer

Methodology Applied

Scientific EffectLattice constant mismatch:

Implementation Method 3

leading to higher electro-luminescent intensity

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS9041032B2Light emitting diode having strain-enhanced well layer

Publication Date: 2015.05.26 SEOUL VIOSYS CO LTD

AI summary

An exemplary embodiment of the present invention includes a light emitting diode including a strain-enhanced well layer. The light emitting diode includes an n-contact layer, an active layer having a barrier layer and a well layer, a p-contact layer, and a strain-enhancing layer configured to enhance a strain applied to the well layer.