InGaN LED Structure With Stress Relaxation for Micro-LED Efficiency
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Solution Overview
Problem
Miniaturization of LEDs leads to reduced light emission efficiency and increased lattice defects due to lattice mismatch issues with nitride-based materials, making it challenging to produce high-efficiency long-wavelength light emission in micro or nano LEDs.
Innovation Solution
A light emitting device structure is developed with a stress relaxation layer between a nitride semiconductor layer and an active layer, where the active layer includes InGaN and has an indium content of 20% or more, and a superlattice structure with thin film layers of 10 nm or less, to mitigate lattice mismatch and enhance crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the size of LED is reduced to micro or nano unit, then the miniaturization is achieved, but the light emission efficiency is lowered
Solution Approach 1:
The patent changes the material composition parameter by incorporating InGaN alloy with varying indium content (20% or more) in the active layer, which enables long-wavelength light emission while maintaining efficiency in miniaturized LEDs. The stress relaxation layer with intermediate lattice constant also represents a parameter change to mitigate lattice mismatch effects that become more pronounced at smaller scales.
2Illumination intensity
If the content of In is increased in nitride-based material, then the long-wavelength light emission is achieved, but the lattice defects are increased due to lattice constant difference with n-GaN layer
Solution Approach 1:
The stress relaxation layer acts as an intermediary between the n-GaN layer and the InGaN active layer. It has a lattice constant that is intermediate between these two layers, gradually transitioning the lattice constant to reduce the abrupt mismatch. This mediator layer prevents dislocation propagation and reduces lattice defects while allowing high indium content (20% or more) in the active layer for long-wavelength emission.
3Illumination intensity
If phosphide-based material is used for long-wavelength light extraction, then the light emission is achieved, but the internal quantum efficiency decreases as the LED size decreases
Solution Approach 1:
The patent uses composite material structure combining n-GaN layer, InGaN stress relaxation layer, and InGaN active layer with 20% or more indium content. This nitride-based composite structure maintains high internal quantum efficiency in miniaturized LEDs while achieving long-wavelength light extraction, overcoming the limitations of phosphide-based materials whose efficiency deteriorates at small sizes.
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 effectively reduces lattice defects and improves light emission efficiency for long-wavelength light, maintaining high efficiency even in miniaturized LED sizes by relieving stress through the stress relaxation layer and optimizing the active layer's indium content and structure.
Implementation Method 1
a stress relaxation layer interposed between the first nitride semiconductor layer and the active layer and having a third lattice constant between the first lattice constant and the second lattice constant
Implementation Method 2
an active layer provided on the first nitride semiconductor layer and having a second lattice constant greater than the first lattice constant, the active layer including a nitride semiconductor material including indium
Data Source
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AI summary
A light emitting device includes a light emitting device includes: a first nitride semiconductor layer doped with an n-type dopant and having a first lattice constant; an active layer provided on the first nitride semiconductor layer and having a second lattice constant greater than the first lattice constant, the active layer including a nitride semiconductor material including indium; a stress relaxation layer interposed between the first nitride semiconductor layer and the active layer and having a third lattice constant between the first lattice constant and the second lattice constant, the stress relaxation layer including a nitride semiconductor material including indium; and a second nitride semiconductor layer provide on the active layer and doped with a p-type dopant, wherein the active layer includes: an upper active region provided on an upper surface of the stress relaxation layer, and a side active region provided on a side surface of the stress relaxation layer.