UV Light Emitting Device Nanorod Buffer Layer Extraction
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Solution Overview
Problem
Semiconductor ultraviolet light emitting devices face challenges in achieving high-quality crystal structures and low light extraction efficiency due to crystal defects and high energy absorption of ultraviolet light, particularly in nitride semiconductor materials like aluminum nitride (AlN).
Innovation Solution
The device incorporates a substrate with a buffer layer featuring nanorods and voids, a first conductive nitride layer, and an active layer with a quantum well structure, where the nanorods are arranged in a hexagonal closet packing configuration and the voids are maintained to enhance light extraction efficiency and crystal quality through epitaxial lateral overgrowth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum nitride (AlN) is used as the semiconductor material for ultraviolet light emitting devices, then the device can emit ultraviolet light, but crystal defects occur and high-quality crystal structure cannot be obtained
Solution Approach 1:
The buffer layer is segmented into multiple AlN layers with different thicknesses and compositions, arranged in a specific sequence. This segmentation allows each layer to serve different functions: some layers provide crystal template, others provide strain compensation, collectively reducing crystal defects and improving overall crystal quality
Solution Approach 2:
The patent uses composite buffer layer structures combining multiple AlN layers with varying aluminum nitride content and thicknesses. This composite approach enables optimization of crystal growth conditions at different depths, reducing dislocation density and improving crystal quality while maintaining ultraviolet light emission capability
2Use of energy by moving object
If ultraviolet light is used, then high energy light emission is achieved, but light extraction efficiency is relatively low due to high absorption by semiconductor
Solution Approach 1:
The buffer layer incorporates porous AlN structures with controlled porosity, creating air-semiconductor interfaces that reduce total internal reflection and improve light extraction efficiency. The porous structure provides multiple light extraction pathways, reducing the impact of semiconductor absorption on ultraviolet light
Solution Approach 2:
The patent introduces localized structural variations in the buffer layer, including regions with different porosity, thickness, and composition. These local quality variations create favorable conditions for light extraction at specific locations, compensating for the high absorption characteristics of semiconductor materials in the ultraviolet range
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 configuration significantly improves light extraction efficiency and crystal quality, maximizing light output while minimizing crystal defects, particularly in the ultraviolet light range from 250 nm to 300 nm.
Implementation Method 1
a buffer layer disposed on the substrate and comprising a plurality of nanorods between which a plurality of voids are formed
Implementation Method 2
an active layer disposed on the first conductive nitride layer and having a quantum well including AlxInyGa1-x-yN
Data Source
AI summary
A semiconductor ultraviolet light emitting device includes: a substrate; a buffer layer disposed on the substrate and comprising a plurality of nanorods between which a plurality of voids are formed; a first conductive nitride layer disposed on the buffer layer and having a first conductive AlGaN layer; an active layer disposed on the first conductive nitride layer and having a quantum well including AlxInyGa1-x-yN (0≤x+y≤1, 0≤y<0.15); and a second conductive nitride layer disposed on the active layer and having a second conductive AlGaN layer, in which the plurality of nanorods satisfy 3.5≤n(λ)×D/λ≤5.0, where λ represents a wavelength of light generated by the active layer, n(λ) represents a refractive index of the plurality of nanorods at a wavelength of λ, and D represents diameters of the plurality of nanorods.