InGaN Template with Spatially Restricted Misfit Dislocations

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Nitride-based devices grown coherently suffer from poor performance due to dislocations that cause strain and polarization effects, limiting the growth of high In-composition InGaN layers and devices like LEDs and LDs.

Innovation Solution

A dislocation-free high-quality template with a relaxed lattice constant is achieved by spatially restricting misfit dislocations around heterointerfaces, allowing for the growth of high In-composition InGaN quantum wells on semipolar planes, which reduces strain and improves device performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If nitride-based devices are grown coherently without misfit dislocations, then device performance is maintained, but the growth of high In-composition InGaN layers is limited due to strain and polarization effects

Engineering Contradiction:

Improvedevice performanceVSAvoidgrowth of high In-composition InGaN layers

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments the device structure into distinct regions: a template layer with controlled misfit dislocations and a device layer grown on top. This segmentation allows the template to absorb strain through localized dislocations while the device layer remains dislocation-free and coherent, enabling high In-composition growth without compromising device performance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The template layer acts as an intermediary between the substrate and the device layer. It is deliberately designed to contain misfit dislocations that relieve strain, serving as a buffer that enables subsequent coherent growth of high In-composition InGaN layers without the strain and polarization effects that would otherwise limit such growth

Inventive Principle:

Principle #24Intermediary (Mediator)

2Illumination intensity

If high In-composition InGaN layers are grown to achieve desired optical properties, then light emission characteristics improve, but strain and polarization effects worsen due to lattice mismatch

Engineering Contradiction:

Improvelight emission characteristicsVSAvoidstrain and polarization effects

Core Design Contradiction:

Illumination intensityVSStress or pressure

Solution Approach 1:

The patent applies preliminary action by growing a template layer with controlled misfit dislocations before growing the high In-composition InGaN device layer. This preliminary template layer pre-relieves the strain that would otherwise accumulate during subsequent high In-composition layer growth, enabling improved light emission characteristics without excessive strain and polarization effects

Inventive Principle:

Principle #10Preliminary action

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

This approach enables the growth of high In-composition InGaN layers and devices with improved light emission characteristics, such as green LEDs and LDs, by eliminating dislocations and strain, resulting in enhanced performance and efficiency.

Implementation Method 1

spatially restricted misfit dislocations (MDs) around heterointerfaces... relaxed lattice constants... Misfit dislocations at the heterointerface

Methodology Applied

Scientific EffectLattice relaxation through misfit dislocations: Deformation

Data Source

PatentUS9159553B2Semipolar or nonpolar nitride-based devices on partially or fully relaxed alloys with misfit dislocations at the heterointerface

Publication Date: 2015.10.13 RGT UNIV OF CALIFORNIA

AI summary

A dislocation-free high quality template with relaxed lattice constant, fabricated by spatially restricting misfit dislocation(s) around heterointerfaces. This can be used as a template layer for high In composition devices. Specifically, the present invention prepares high quality InGaN templates (In composition is around 5-10%), and can grow much higher In-composition InGaN quantum wells (QWs) (or multi quantum wells (MQWs)) on these templates than would otherwise be possible.