AlN-Based UV LED Structure for High External Quantum Efficiency
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Solution Overview
Problem
Nitride UV LED devices have external quantum efficiencies of 5% or less, particularly at wavelengths of 300 nm or less, which are impractical for sterilizing applications due to low light-emitting efficiency.
Innovation Solution
A light-emitting device structure is developed using an AlN-based group III nitride single crystal with a high-concentration n-type AlGaN layer, a multi-quantum well structure, an i-type AlxGa1-xN final barrier layer, and an electron blocking layer formed of a p-type or i-type AlzGa1-zN, optimized for thickness and composition to reduce piezoelectric field effects and threading dislocation, enhancing emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional nitride UV LED structures are used, then device simplicity is maintained, but external quantum efficiency remains 5% or less (particularly 2% or less at 300 nm or less wavelength)
Solution Approach 1:
The device is divided into multiple functional layers including high-concentration n-type group III nitride layer, multi-quantum well structure with n-type or i-type barrier and well layers, i-type final barrier layer, p-type group III nitride layer, and electron blocking layer. This segmentation allows each layer to perform its specific function optimally, resulting in external quantum efficiency exceeding 5% (particularly exceeding 2% at 300 nm or less wavelength).
Solution Approach 2:
Different layers are assigned different doping types and compositions tailored to their specific functions: high-concentration n-type doping in the contact layer for electron injection, undoped or lightly doped i-type regions for carrier confinement, and p-type regions for hole injection. The multi-quantum well structure uses alternating high-Al composition barrier layers and lower-Al composition well layers to create localized potential wells for carrier confinement.
2Illumination intensity
If AlGaInN quaternary mixed crystal is used for UV emission, then emission peak wavelength can be set at 360 nm or less, but internal quantum efficiency remains similar to InGaN layer without significant improvement
Solution Approach 1:
The invention optimizes the composition parameters of the AlGaN-based multi-quantum well structure, specifically controlling the Al composition ratio to achieve deep UV emission at 360 nm or less while maintaining high internal quantum efficiency. The high-concentration n-type doping and the specific structure of the electron blocking layer further optimize carrier injection and confinement, resulting in emission intensity that exceeds conventional structures.
Solution Approach 2:
The i-type final barrier layer and electron blocking layer act as intermediary structures between the multi-quantum well active region and the p-type contact layer. These intermediary layers facilitate efficient carrier transport and confinement while reducing non-radiative recombination, thereby improving internal quantum efficiency and overall emission intensity.
3Stability of the object's composition
If thin well layer (1.3 nm to 2.6 nm) is used to suppress piezoelectric field effect, then emission characteristic perpendicular to substrate is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies a particular thickness range for the well layer (1.3 nm to 2.6 nm, preferably 2.0 nm or less) to suppress the piezoelectric field effect and achieve emission perpendicular to the substrate surface. This parameter optimization ensures stable emission characteristics while being achievable with conventional manufacturing precision.
4Stability of the object's composition
If i-type final barrier layer with thickness 2 nm to 12.6 nm is used, then asymmetry of uppermost quantum well is suppressed and peak split is prevented, but layer structure complexity increases
Solution Approach 1:
The invention introduces an i-type final barrier layer with optimized thickness (2 nm to 12.6 nm, preferably 10 nm or less) between the multi-quantum well structure and the p-type contact layer. This layer suppresses asymmetry of the uppermost quantum well under applied voltage, prevents peak splitting, and maintains stable emission characteristics. The specific doping type and thickness parameters are optimized to achieve this effect with minimal additional structural complexity.
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 significantly improves the light-emitting efficiency of deep-UV light-emitting devices, achieving higher external quantum efficiencies and practical emission characteristics suitable for sterilizing applications.
Implementation Method 1
a multi quantum well structure formed of an n-type or i-type group III nitride barrier layer and an n-type or i-type group III nitride well layer
Implementation Method 2
an electron blocking layer formed between the i-type group III nitride final barrier layer and the p-type group III nitride layer
Implementation Method 3
The thickness of the well layer of the AlyGa1-yN layer is set to preferably 1.3 nm to 2.6 nm, more preferably 2.0 nm or less. Such thin well layer suppresses the piezoelectric field effect in the AlyGa1-yN layer, and achieves such an emission characteristic that light is emitted from the direction perpendicular to the substrate surface.
Data Source
AI summary
Devices and techniques related to UV light-emitting devices that can be implemented in ways that improve the light-emitting efficiency of an UV light-emitting device using a group III nitride semiconductor.