Nitride Semiconductor Light Emitting Device Quantum Barrier Superlattice
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Solution Overview
Problem
Nitride semiconductor light emitting devices face a decrease in recombination efficiency due to lattice constant mismatch and piezoelectric fields at the interface between InGaN quantum well layers and GaN quantum barrier layers, making it challenging to grow high-quality AlInGaN quantum barrier layers with optimal processing conditions.
Innovation Solution
The solution involves alternating AlGaN and InGaN layers, starting and ending with InGaN, or alternating InGaN and GaN layers, to form a quantum barrier layer, which reduces lattice constant mismatch and generates a super lattice structure to enhance light emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AlInGaN quantum barrier layer is grown to reduce lattice constant mismatch, then recombination efficiency is improved, but crystalline quality deteriorates due to conflicting processing conditions for Al and In atom penetration
Solution Approach 1:
The quantum barrier layer is segmented into multiple thin layers alternating between AlGaN and InGaN materials, forming a superlattice structure. This segmentation allows each layer to be grown under optimized conditions for its specific material composition, avoiding the crystalline quality degradation that occurs when attempting to grow a homogeneous AlInGaN layer under conflicting processing conditions.
Solution Approach 2:
The patent employs composite material structure by combining AlGaN and InGaN layers in an alternating sequence. This composite approach leverages the advantages of both materials: AlGaN provides high bandgap and effective electron confinement, while InGaN layers reduce lattice mismatch with the InGaN quantum well. The composite superlattice structure achieves both high recombination efficiency and excellent crystalline quality.
2Reliability
If GaN quantum barrier layer is used, then high energy band gap is achieved, but lattice constant mismatch with InGaN quantum well layer increases
Solution Approach 1:
The quantum barrier structure implements local quality by using different material compositions in different regions. The AlGaN layers provide high bandgap regions for electron confinement, while the InGaN layers provide lattice-matched regions adjacent to the InGaN quantum well. This spatial variation in material properties simultaneously achieves high energy bandgap and reduced lattice mismatch.
Solution Approach 2:
The InGaN layers act as intermediary layers between the InGaN quantum well and the AlGaN barrier layers. These intermediary layers reduce the lattice constant mismatch at the interface, serving as a transition zone that facilitates better epitaxial growth and reduces dislocation density, while the AlGaN layers maintain the high bandgap necessary for effective electron confinement.
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 approach increases the overlap between electron and hole wave functions, reduces piezoelectric fields, and effectively confines electrons within the quantum well layer, thereby improving light emitting efficiency.
Implementation Method 1
reduces lattice constant mismatch between a quantum well layer formed of InGaN and a quantum barrier layer
Implementation Method 2
effectively confines electrons within the quantum well layer
Implementation Method 3
a piezoelectric field occurs within the quantum well layers due to a lattice constant mismatch at the interface between the InGaN quantum well layers 12a and the GaN quantum barrier layers 12b
Implementation Method 4
light is emitted as electrons supplied from the n-type nitride semiconductor layer 11 and holes supplied from the p-type nitride semiconductor 13 are recombined in the active layer 12
Data Source
AI summary
There is provided a nitride semiconductor light emitting device. A nitride semiconductor light emitting device according to an aspect of the invention may include: an n-type nitride semiconductor layer provided on a substrate; an active layer provided on the n-type nitride semiconductor layer, and including quantum barrier layers and quantum well layers; and a p-type nitride semiconductor layer provided on the active layer, wherein each of the quantum barrier layers includes a plurality of InxGa(1-x)N layers (0<x<1) and at least one AlyGa(1-y)N layer (0≦y<1), and the AlyGa(1-y)N layer is stacked between the InxGa(1-x)N layers.