Nitride Semiconductor Light Emitting Device with Composite Barrier
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Solution Overview
Problem
Current nitride semiconductor light emitting devices face challenges in achieving high crystallinity and light output due to limitations in crystal growth techniques, leading to increased crystal defects, reduced light efficiency, and reliability issues.
Innovation Solution
A nitride semiconductor light emitting device with an active layer comprising an InGaN well layer and a multilayer barrier layer, formed using a specific fabrication method that includes a buffer layer, a GaN-based layer, and electrode layers to enhance crystallinity and light emission, along with a p-GaN layer and n-type nitride semiconductor layers to improve current injection and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single quantum well structure or multiple quantum well structure with InGaN/GaN lamination is used, then light emission efficiency can be improved, but crystal defects such as pits increase and crystallinity deteriorates
Solution Approach 1:
The patent employs a composite barrier layer structure consisting of GaN and AlGaN layers in alternating sequence. This composite material approach allows the GaN layers to provide good crystallinity and the AlGaN layers to suppress pit formation, thereby resolving the contradiction between light emission efficiency and crystallinity.
Solution Approach 2:
The barrier layer is segmented into multiple thin layers (GaN and AlGaN alternating) rather than using a single thick barrier layer. This segmentation allows each thin layer to maintain good crystallinity while the alternating composition provides continuous suppression of pit formation throughout the quantum well structure.
2Productivity
If the number of periods in multiple quantum well structure is increased, then light efficiency should increase, but the number of crystal defects such as pits increases
Solution Approach 1:
By using composite GaN/AlGaN barrier layers, each period in the multiple quantum well structure benefits from pit suppression. This allows increasing the number of periods to improve light efficiency without proportionally increasing crystal defects, as each replicated unit maintains high crystallinity.
3Ease of manufacture
If Mg dopants are diffused into pits of light emission layer, then interface between GaN barrier layer and p-GaN breaks down, but light efficiency and stability are affected
Solution Approach 1:
The AlGaN layers in the composite barrier structure act as diffusion barriers that prevent Mg dopants from reaching and accumulating in pit regions. This maintains the integrity of the GaN barrier layer/p-GaN interface, preventing breakdown and ensuring long-term device stability.
4Reliability
If very thin transparent resistive metals are used to decrease contact resistance, then current injection efficiency increases, but light transmission loss increases
Solution Approach 1:
The patent optimizes the thickness parameter of transparent conductive oxide layers (such as ITO or ZnO) to achieve the minimum thickness required for acceptable electrical conductivity while maximizing light transmission. This parameter optimization resolves the trade-off between contact resistance and light transmission loss.
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 proposed solution improves the crystallinity and light output of the nitride semiconductor light emitting device, enhancing its reliability and internal quantum efficiency while reducing contact resistance and operating voltage.
Implementation Method 1
a polycrystalline thin film of AlyGa1-yN is grown as a buffer layer on the sapphire substrate or the SiC substrate at a low growth temperature
Implementation Method 2
an undoped GaN layer, an n-GaN layer doped with silicon (Si) or a combination of both is grown on the buffer layer at a high temperature to form a n-GaN layer
Implementation Method 3
The p-GaN layer is formed by doping Mg atoms during crystal growth. The Mg atoms implanted as a doping source during crystal growth should be substituted with Ga positions to act as a p-GaN layer
Implementation Method 4
they are combined with a hydrogen gas separated from the source and a carrier gas to form a Mg—H complex in a GaN crystalline layer and become a high resistance material about 10Ω
Data Source
AI summary
A nitride semiconductor light emitting device comprises a first nitride semiconductor layer, an active layer of a single or multiple quantum well structure formed on the first nitride semiconductor layer and including an InGaN well layer and a multilayer barrier layer, and a second nitride semiconductor layer formed on the active layer. A fabrication method of a nitride semiconductor light emitting device comprises: forming a buffer layer on a substrate, forming a GaN layer on the buffer layer, forming a first electrode layer on the GaN layer, forming an InxGa1-xN layer on the first electrode layer, forming on the first InxGa1-xN layer an active layer including an InGaN well layer and a multilayer barrier layer for emitting light, forming a p-GaN layer on the active layer, and forming a second electrode layer on the p-GaN layer.