Strain releasing layer in nitride semiconductor LED
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Solution Overview
Problem
Conventional nitride semiconductor LEDs suffer from strain-induced defects in the multiple quantum well structure due to lattice mismatch between GaN and InGaN, leading to reduced light-emitting efficiency.
Innovation Solution
The introduction of a strain releasing layer with specific Indium and Aluminum compositions between differently formed portions of the multiple quantum well structure, along with varying Indium concentrations in the well layers, helps alleviate strain and improve epitaxial quality, reducing defects and enhancing light-emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a multiple quantum well structure with GaN barrier layers and InGaN well layers is used to increase light-emitting efficiency, then the light-emitting efficiency is improved, but strain-induced defects occur due to lattice mismatch between GaN and InGaN
Solution Approach 1:
The multiple quantum well structure is divided into a first portion and a second portion with different Indium concentrations. The first portion has lower Indium concentration and the second portion has higher Indium concentration, allowing gradual strain release while maintaining light-emitting efficiency.
Solution Approach 2:
Different regions of the multiple quantum well structure are assigned different Indium concentrations tailored to their specific functions. The first portion uses lower Indium concentration for strain management, while the second portion uses higher Indium concentration for optimized light emission.
2Use of energy by moving object
If Indium concentration in well layers is increased to improve light-emitting efficiency, then the light-emitting efficiency is improved, but strain in the multiple quantum well structure increases causing more defects
Solution Approach 1:
The well layers are segmented into two portions with different Indium concentrations. This segmentation allows the structure to accommodate higher overall Indium content for improved efficiency while distributing strain across regions with progressively increasing Indium concentrations.
Solution Approach 2:
The Indium concentration parameter is varied spatially across the multiple quantum well structure, transitioning from lower concentrations in the first portion to higher concentrations in the second portion, optimizing both strain management and light emission.
Data Source
AI summary
A light-emitting device comprises a first type semiconductor layer, a multi-quantum well structure on the first type semiconductor layer, and a second type semiconductor layer on the multi-quantum well structure, wherein the multi-quantum well structure comprises a first portion near the first type semiconductor layer, a second portion near the second type semiconductor layer, and a strain releasing layer between the first portion and the second portion and comprising a first layer including Indium, a second layer including Aluminum on the first layer, and a third layer including Indium on the second layer, wherein the Indium concentration of the third layer is higher than that of the first layer.