Mechanically Compliant LED Layers for Strain Relaxation

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Solution Overview

Problem

The growth of long-wavelength III-nitride light-emitting diodes (LEDs) is challenging due to high defect densities and strain-induced issues, which reduce internal quantum efficiency and make it difficult to incorporate indium, leading to lattice mismatch and defect creation.

Innovation Solution

A method involving a mechanically-compliant layer to relax strain energy, reducing extended defect density and enhancing leakage resistance in the light-emitting region, allowing for higher indium incorporation and improved quantum efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a Gallium Nitride (GaN) matrix is used to produce III-nitride LEDs, then the structural stability is improved, but the strain induced by lattice difference with Indium Gallium Nitride (InGaN) light-emitting layers causes defect incorporation and reduces Indium incorporation

Engineering Contradiction:

Improvestructural stabilityVSAvoiddefect density

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent segments the GaN matrix into two distinct parts: a rigid GaN layer providing structural stability, and a separate mechanically-compliant layer that can relax strain. This segmentation allows the rigid portion to maintain composition stability while the compliant portion absorbs strain energy, preventing defect incorporation in the light-emitting region.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mechanically-compliant layer acts as an intermediary between the rigid GaN matrix and the InGaN light-emitting layers. This intermediary layer absorbs the strain energy generated by lattice mismatch, preventing it from propagating into the light-emitting region and causing defects, while still allowing the overall structure to maintain stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If a high amount of Indium (In) is incorporated for long-wavelength light emission, then the emission wavelength is improved, but the strain increases leading to defect creation and reduced internal quantum efficiency

Engineering Contradiction:

Improveemission wavelengthVSAvoidinternal quantum efficiency

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent changes the mechanical parameter of the GaN matrix by introducing a mechanically-compliant layer with different elastic properties. This parameter change allows the structure to accommodate high Indium content in the InGaN layers for long-wavelength emission without accumulating strain that would lead to defects and reduced internal quantum efficiency.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If the lattice mismatch between GaN and InGaN layers is addressed by increasing Indium content, then the long-wavelength emission is improved, but the strain energy increases causing defect incorporation

Engineering Contradiction:

Improveemission wavelength precisionVSAvoidstrain energy

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful strain energy generated by lattice mismatch into a beneficial effect. The mechanically-compliant layer is designed to absorb and dissipate this strain energy through controlled deformation, preventing defect formation while maintaining the high Indium content necessary for precise long-wavelength emission control.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach results in a significant reduction in defect density, increased leakage resistance, and enhanced internal quantum efficiency, enabling efficient long-wavelength emission with reduced strain effects.

Implementation Method 1

performing a relaxation operation to facilitate a release of strain energy in the second layer by the mechanically-compliant layer

Methodology Applied

Scientific EffectStrain relaxation: Stress Relaxation

Data Source

PatentUS20240030380A1Light emitting devices with reduced strain

Publication Date: 2024.01.25 GOOGLE LLC

AI summary

In a general aspect, a method for producing an optoelectronic device includes forming a mechanically-compliant layer on a substrate, and forming a second layer, the mechanically-compliant layer being disposed between the second layer and the substrate. The method also includes performing a relaxation operation to facilitate a release of strain energy in the second layer by the mechanically-compliant layer. The mechanically-compliant layer, the second layer and the relaxation operation are configured such that a surface of the second layer has an extended defect density below a predetermined value. The method also includes forming a light-emitting region, the second layer being disposed between the light-emitting region and the substrate. The extended defect density being below the predetermined value results in a leakage resistance in an active region of the light-emitting region that is higher than 10 milliohms per centimeter-squared (mOhm/cm2).