LED Nucleation Layer for Directional Light Extraction

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Solution Overview

Problem

Direct light emitting diodes (LEDs) based on patterned sapphire substrates suffer from low luminance levels and broad angular emission patterns due to their geometrical features, which can be mitigated but result in reduced light extraction efficiency when side-coating materials are used to prevent light escape.

Innovation Solution

The implementation of a nucleation layer comprising a III-nitride material on a substrate before patterning, followed by a patterned dielectric layer with features and spaces, allows for selective area deposition of a III-nitride layer, enhancing light extraction efficiency and luminance by controlling light emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If side-coating materials are used to prevent light escaping from the sides of the chip, then light emission directionality is improved, but light extraction efficiency is significantly reduced

Engineering Contradiction:

Improvelight emission directionalityVSAvoidlight extraction efficiency

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The invention extracts and removes the side-coating materials from the LED structure entirely. By using a patterned sapphire substrate with controlled light emission from the top surface only, the patent eliminates the need for side-coating materials that trapped light and reduced extraction efficiency. The sapphire substrate's natural optical properties are leveraged to achieve directional emission without the harmful side-coats.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of adding side-coating materials to control light emission direction (the conventional approach), the invention inverts the strategy by using a patterned substrate structure that inherently directs light upward from the top surface. The patterned sapphire substrate creates geometric constraints that naturally enforce top-surface emission without requiring additional reflective or absorptive coating layers.

Inventive Principle:

Principle #13The other way round (Inversion)

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 increases light extraction efficiency, brightness, and angular directionality, resulting in higher luminance and focused light emission within a narrow angular cone, improving the performance of LEDs without the need for side-coating materials.

Implementation Method 1

epitaxial growing a III-nitride layer on the patterned surface

Methodology Applied

Scientific EffectEpitaxy: Epitaxy

Implementation Method 2

nucleation layer comprising a III-nitride material on a substrate before patterning

Methodology Applied

Scientific EffectNucleation: Nucleation

Data Source

PatentUS11264530B2Light emitting diode (LED) devices with nucleation layer

Publication Date: 2022.03.01 LUMILEDS SINGAPORE PTE LTD

AI summary

Described are light emitting diode (LED) devices having patterned substrates and methods for effectively growing epitaxial III-nitride layers on them. A nucleation layer, comprising a III-nitride material, is grown on a substrate before any patterning takes place. The nucleation layer results in growth of smooth coalesced III-nitride layers over the patterns.