GaN Substrate Light Extraction Structures for LED Efficiency

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Solution Overview

Problem

Gallium nitride-based LEDs grown on sapphire substrates face limitations such as high manufacturing costs, reduced light output, and efficiency issues due to lattice mismatch and dislocation density, as well as the droop phenomenon and current crowding problems.

Innovation Solution

A light-emitting device using a GaN substrate with a thickness of 80 μm or more, featuring light extraction structures on one surface and a doping concentration gradient, where the substrate has a high area coverage of light extraction structures to enhance light extraction efficiency and emission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a sapphire substrate is used for growing gallium nitride-based LEDs, then the LED can be manufactured with existing processes, but the thermal conductivity is low and manufacturing costs cannot be reduced through size reduction

Engineering Contradiction:

Improvemanufacturing process compatibilityVSAvoidthermal conductivity

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent changes the substrate material parameter from sapphire to GaN substrate, which fundamentally alters the thermal conductivity property. The GaN substrate provides superior thermal conductivity compared to sapphire, enabling better heat dissipation and allowing for size reduction while maintaining manufacturing feasibility.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If a sapphire substrate is used, then existing manufacturing processes can be utilized, but light output and chip characteristics are degraded

Engineering Contradiction:

Improvemanufacturing process compatibilityVSAvoidlight output

Core Design Contradiction:

Ease of manufactureVSIllumination intensity

Solution Approach 1:

The substrate material parameter is changed from sapphire to GaN substrate, which improves the light output characteristics. The GaN substrate reduces dislocation density and improves crystal quality, leading to enhanced light emission efficiency and chip performance.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional substrates are used, then manufacturing is simpler, but lattice mismatch occurs leading to high dislocation density

Engineering Contradiction:

Improvesubstrate availabilityVSAvoidlattice mismatch

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the substrate material parameter to GaN substrate, which has a lattice constant that closely matches gallium nitride. This eliminates lattice mismatch and dramatically reduces dislocation density, improving the crystalline quality of the LED structure.

Inventive Principle:

Principle #35Parameter changes

4Illumination intensity

If current density is increased to improve LED performance, then brightness increases, but internal quantum efficiency decreases due to droop phenomenon

Engineering Contradiction:

ImprovebrightnessVSAvoidinternal quantum efficiency

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The patent applies local quality by creating a doping concentration gradient in the GaN substrate, with different doping levels in different regions. This gradient structure optimizes carrier distribution and reduces the droop phenomenon, maintaining high internal quantum efficiency even at increased current densities.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the doping concentration parameter by introducing a gradient structure with varying doping levels across the substrate. This parameter modification optimizes electrical properties and reduces efficiency droop, allowing sustained high brightness output.

Inventive Principle:

Principle #35Parameter changes

5Power

If current density is increased, then LED output increases, but current crowding problems occur reducing reliability

Engineering Contradiction:

ImproveLED outputVSAvoidcurrent distribution uniformity

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent applies local quality by implementing a doping concentration gradient in the GaN substrate, where doping levels vary spatially. This creates more uniform current distribution across the LED active region, preventing current crowding and improving reliability while maintaining high power output.

Inventive Principle:

Principle #3Local quality

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

Prevents lattice mismatch, increases light extraction and emission efficiency, and improves current distribution, leading to enhanced performance and reliability of the LED device.

Implementation Method 1

light extraction structures disposed on the other surface of the substrate

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

Gallium nitride-based LEDs grown on a sapphire substrate... lattice mismatch and low dislocation density

Methodology Applied

Scientific EffectLattice mismatch:

Data Source

PatentUS10553756B2Light emitting device

Publication Date: 2020.02.04 SUZHOU LEKIN SEMICON CO LTD

AI summary

An embodiment of the present invention includes: a gallium nitride substrate; and a light-emitting structure disposed on the other surface of the substrate, wherein the substrate includes a plurality of light extraction structures formed on one surface thereof, the thickness of the substrate is 80 μm or more, and the average height of the plurality of light extraction structures is 10 μm or more.