Nitride LED Active Layer Structure for High-Current Quantum Efficiency

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Solution Overview

Problem

Nitride semiconductor light emitting devices experience a rapid decrease in internal quantum efficiency as applied current increases, necessitating a method or structure to enhance efficiency while emitting light of specific wavelengths.

Innovation Solution

The device incorporates a P-type and N-type nitride semiconductor layer configuration with alternating InGaN and GaN strain reducing layers, an active layer with InGaN well and barrier layers, and an AlGaN layer, along with an intermediate lattice layer to manage strain and maintain high indium composition ratios, thereby optimizing light emission efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If the applied current is increased to enhance light emission intensity, then the illumination intensity is improved, but the internal quantum efficiency rapidly decreases

Engineering Contradiction:

Improvelight emission intensityVSAvoidinternal quantum efficiency

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the compositional parameters of the semiconductor layers by introducing an AlGaN layer with aluminum content (0.05 ≤ x ≤ 0.50) between the InGaN well layer and GaN barrier layer. This compositional parameter change modifies the band structure and carrier confinement, enabling high internal quantum efficiency to be maintained even at high current densities, thus resolving the contradiction between illumination intensity and quantum efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite light emitting layer structure combining InGaN well layer, AlGaN intermediate layer, and GaN barrier layer. This composite structure leverages the complementary properties of each material: InGaN for light emission, AlGaN for carrier confinement and strain management, and GaN for high breakdown field, achieving both high intensity and high efficiency simultaneously

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If the indium composition ratio is increased to emit long-wavelength light, then the emission wavelength is extended, but the lattice mismatch and strain increase

Engineering Contradiction:

Improveemission wavelengthVSAvoidlattice mismatch

Core Design Contradiction:

Illumination intensityVSStability of the object's composition

Solution Approach 1:

The AlGaN layer acts as an intermediary between the InGaN well layer and GaN barrier layer. It has a lattice constant intermediate between InGaN and GaN, providing a gradual transition that reduces lattice mismatch and strain accumulation, enabling stable growth of high-indium-content well layers for long-wavelength emission

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes the可调性 (tunability) of the AlGaN layer's aluminum composition ratio (0.05 ≤ x ≤ 0.50) to optimize the lattice constant gradient. By adjusting this parameter, the intermediate layer can be tailored to match specific InGaN compositions, managing lattice mismatch while maintaining the desired emission wavelength

Inventive Principle:

Principle #35Parameter changes

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 configuration significantly enhances the internal quantum efficiency and emission wavelength stability, particularly for long-wavelength light emission, such as red and orange, by reducing strain and maintaining high indium composition ratios in the InGaN well layers.

Implementation Method 1

an InGaN well layer and a barrier layer having a band gap wider than a band gap of the InGaN well layer are stacked

Methodology Applied

Scientific EffectBand gap difference:

Implementation Method 2

a first strain reducing layer provided between the N-type nitride semiconductor layer and the active layer, the first strain reducing layer including a first InGaN film and a first GaN film alternately stacked

Methodology Applied

Scientific EffectStrain reduction:

Implementation Method 3

an intermediate lattice layer provided between the InGaN well layer and the AlGaN layer, the intermediate lattice layer including a nitride single crystal having a lattice larger than a first lattice of the InGaN well layer and smaller than a second lattice of the AlGaN layer

Methodology Applied

Scientific EffectLattice matching:

Implementation Method 4

A semiconductor light emitting device may generate light of a specific wavelength by recombination of electrons and holes

Methodology Applied

Scientific EffectElectron-hole recombination:

Data Source

PatentUS20240021756A1Nitride semiconductor light emitting device

Publication Date: 2024.01.18 SAMSUNG ELECTRONICS CO LTD

AI summary

A nitride semiconductor light emitting device includes an active layer provided between P-type and N-type nitride semiconductor layers, a first strain reducing layer including first InGaN films and first GaN films alternately stacked between the N-type nitride semiconductor layer and the active layer, and a second strain reducing layer including a second InGaN film and a second GaN film alternately stacked between the first strain reducing layer and the active layer. The active layer includes an InGaN well layer, a barrier layer, an AlGaN layer between the InGaN well layer and the barrier layer, and an intermediate lattice layer between the InGaN well layer and the AlGaN layer The intermediate lattice layer including a nitride single crystal having a lattice larger than a first lattice of the InGaN well layer and smaller than a second lattice of the AlGaN layer.