AlGaInP LED Light Extraction via Distributed Bragg Reflector

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Solution Overview

Problem

Conventional AlGaInP-based light emitting diodes (LEDs) suffer from low light extraction efficiency due to internal total reflection, with light being reflected at large incidence angles and traveling laterally, reducing emission efficiency.

Innovation Solution

A multilayered light emitting structure with a distributed Bragg reflector (DBR) structure is designed, where the n-type and p-type confinement layers are positioned proximal and distal to the DBR, and each DBR unit has a center reflection wavelength defined by λ+(z−1)λ0, enhancing the reflection of oblique incident light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a conventional DBR structure is used in AlGaInP-based LEDs, then light extraction efficiency is improved, but oblique incident light is reflected at large angles and travels laterally, reducing emission efficiency

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidemission efficiency

Core Design Contradiction:

Loss of energyVSProductivity

Solution Approach 1:

The patent applies local quality by positioning confinement layers at specific locations (proximal and distal to the DBR structure) to create localized refractive index variations. This targeted approach modifies light propagation only in critical regions where oblique light interacts with the DBR, preventing lateral travel while maintaining overall device performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the refractive index parameter by introducing confinement layers with different refractive indices between the active layer and DBR structure. This parameter modification alters the optical path of oblique incident light, enabling better extraction efficiency without the harmful lateral travel effect.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the refractive index is increased in waveguide layers and confinement layers, then light guiding is improved, but light incidence at large angles travels laterally and is absorbed or guided to exit laterally

Engineering Contradiction:

Improvelight guidingVSAvoidlight absorption and lateral exit

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite material structure by combining waveguide layers with confinement layers having different refractive indices. This composite approach creates a multi-layered system where each layer contributes different optical properties, enabling effective light confinement while preventing lateral travel of oblique incident light.

Inventive Principle:

Principle #40Composite materials

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 solution enhances light output by reducing lateral traveling of oblique incident light and increasing light emission efficiency by 5% to 15% from the light emitting surface.

Implementation Method 1

growth of a distributed Bragg reflector (DBR) structure

Methodology Applied

Scientific EffectDistributed Bragg reflection: Bragg Diffraction

Implementation Method 2

internal total reflection

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

A relatively large refractive index is observed among the first and second waveguide layers 130, 150 and the n-type and p-type confinement layers 120, 160

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10930815B2Light emitting device

Publication Date: 2021.02.23 XIAMEN SANAN OPTOELECTRONICS CO LTD

AI summary

A light emitting device includes a light emitting structure and a distributed Bragg reflector (DBR) structure disposed thereon. The light emitting structure includes an n-type confinement layer, an active layer disposed on the n-type confinement layer, and a p-type confinement layer disposed on the active layer opposite to the n-type confinement layer. The n-type and p-type confinement layers are disposed proximal and distal to the DBR structure, respectively. The DBR structure includes first to Nth DBR units. The first and Nth DBR units are disposed proximal and distal to the light emitting structure, respectively. Each of the first to Nth DBR units has a center reflection wavelength defined by λ+(z−1)λ0.