InGaN Well Layer Strain and Composition for Blue LED Efficiency
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Solution Overview
Problem
The quality of InGaN crystal layers in blue LEDs used for white light emission is degraded due to lattice constant mismatch with GaN, leading to reduced light emission efficiency, and existing technologies struggle to achieve high light emission efficiency while maintaining crystallinity.
Innovation Solution
A semiconductor light emitting element with a nitride semiconductor structure, including a first and second semiconductor layer and a light emitting layer with a well layer of InxGa1-xN, where the first semiconductor layer has a tensile strain and the second semiconductor layer has a tensile strain, optimizing the lattice constants and well layer thickness to achieve a desired peak wavelength and high light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a quantum well structure of InGaN/GaN is used for the light emitting layer, then the light emission efficiency can be improved, but the quality of the InGaN crystal layer may be degraded due to lattice constant mismatch
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness of the InGaN well layer (2-5 nm) and the composition ratio of In to Ga. By adjusting these parameters, the lattice mismatch stress is reduced while maintaining the quantum well effect, thus improving crystal quality without sacrificing light emission efficiency
Solution Approach 2:
The patent implements local quality by creating a quantum well structure where the InGaN layer has different properties than the surrounding GaN barrier layers. The well layer is designed with specific thickness and composition to locally confine carriers and enhance light emission, while the overall structure maintains crystal quality through controlled lattice matching
2Illumination intensity
If the In composition ratio is increased to achieve desired peak wavelength, then the light emission characteristics improve, but the lattice constant mismatch increases and crystal quality degrades
Solution Approach 1:
The patent resolves this contradiction by changing multiple parameters simultaneously: reducing the well layer thickness to 2-5 nm and optimizing the In composition ratio. This combination allows achieving the desired peak wavelength (430-470 nm) while maintaining crystal quality by reducing the absolute lattice mismatch distance
3Productivity
If the well layer thickness is reduced to improve carrier confinement, then the light emission efficiency increases, but the crystal quality may be degraded
Solution Approach 1:
The patent applies parameter changes by optimizing the well layer thickness to a specific range (2-5 nm). This thickness is thin enough to provide strong carrier confinement and high light emission efficiency, yet thick enough to maintain crystal quality and avoid excessive lattice mismatch stress
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 emission efficiency by reducing the In composition ratio for a desired peak wavelength, maintaining high crystallinity, and improving carrier confinement, resulting in improved light extraction and thermal dissipation.
Implementation Method 1
a quantum well structure of InGaN/GaN, for example, is used for the light emitting layer
Implementation Method 2
White light is obtained by combining a blue LED (light emitting diode) that emits blue light and a fluorescent substance
Data Source
AI summary
In general, according to one embodiment, a semiconductor light emitting element includes: a first semiconductor layer; a second semiconductor layer; a light emitting layer. The light emitting layer includes a well layer with a thickness of t1 (nanometers). The well layer includes InxGa1-xN having an In composition ratio x higher than 0 and lower than 1. The first semiconductor layer has a tensile strain of not less than 0.02 percent and not more than 0.25 percent in a plane perpendicular to a stacking direction. A peak wavelength λp (nanometers) of light satisfies a relationship of λp=a1+a2×(x+(t1−3.0)×a3). The a1 is not less than 359 and not more than 363. The a2 is not less than 534 and not more than 550. The a3 is not less than 0.0205 and not more than 0.0235.