Double-Sided Sapphire Microlens Array for Uniform Deep UV LED Output
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Solution Overview
Problem
Traditional ultraviolet LED packaging structures suffer from uneven light emission and low light extraction efficiency, which hinders the development of high-performance and high-uniformity deep ultraviolet LEDs.
Innovation Solution
A double-sided microlens array is created using a sapphire glass lens with nano-arrays on both sides, processed through polishing, plasma chemical vapor deposition, photoresist patterning, and etching, and integrated into a deep ultraviolet LED inorganic module packaging device to enhance light refractive index and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional LED packaging structure is used, then device simplicity is maintained, but light extraction efficiency and light emitting uniformity are insufficient
Solution Approach 1:
The packaging structure is segmented into multiple functional layers: sapphire substrate, AlN buffer layer, multiple quantum well active layers, p-type and n-type cladding layers, and contact layers. This segmentation allows optimization of light extraction and electrical properties in each layer independently, achieving high uniformity without excessive overall complexity.
Solution Approach 2:
The patent transitions from planar LED structures to vertically stacked multi-layer heterostructures. By adding the vertical dimension with alternating p-type and n-type layers, the design achieves superior light extraction efficiency and uniformity while maintaining manageable structural complexity through systematic layering.
2Illumination intensity
If complex multi-layer heterostructure is implemented, then light extraction efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The patent systematically varies critical parameters across layers including aluminum composition (5-20% in AlGaInP), layer thicknesses (50-200 nm), and doping concentrations (1e16 to 1e18 atoms/cm³). These parameter changes are optimized to maximize light extraction efficiency while maintaining compatibility with existing semiconductor manufacturing processes.
Solution Approach 2:
The LED structure employs composite materials including AlGaInP quantum well layers combined with GaP barrier layers, and sapphire substrate with AlN buffer layer. These composite material systems enable enhanced light extraction through refractive index mismatch and strain management, achieving high efficiency with manufacturable material combinations.
3Reliability
If deep ultraviolet LED performance is enhanced, then application capability is improved, but light emitting uniformity becomes insufficient
Solution Approach 1:
The patent introduces dynamic carrier confinement through alternating p-type and n-type cladding layers that create potential wells. This dynamic structure confines carriers effectively in the active region while allowing controlled carrier injection and extraction, achieving both high deep UV performance and uniform light emission.
Solution Approach 2:
Different regions of the LED structure are assigned specialized functions: AlN buffer layer for dislocation management, AlGaInP quantum wells for light generation, GaP barriers for carrier confinement, and doped contact layers for electrical injection. This local quality optimization ensures high performance and uniformity in the deep UV wavelength 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
The solution significantly improves light uniformity and intensity by reducing total reflection loss and increasing optical coupling, resulting in higher luminous intensity and reliability of the ultraviolet LED packaging.
Implementation Method 1
depositing a 200 nm thick SiO2 film on the polished surface by plasma chemical vapor deposition at a processing temperature of 300° C.
Implementation Method 2
performing a projection exposure by a mask, and then performing a projection exposure by a stepper lithography machine with an exposure wavelength of 365 nm
Implementation Method 3
transferring a pattern onto the SiO2 film by plasma etching for 1 minute
Implementation Method 4
etching the sapphire glass lens by a strong acid mixture heated to 270° C. for 6 minutes
Implementation Method 5
Based on the refraction principle of geometric optics, light at the interface of two transparent media (such as air and glass) will bend toward the area with high refractive index
Data Source
AI summary
A method for preparing a double-sided microlens array, which is used to prepare a uniform, large-area and easy-to-control microlens array on upper and lower surfaces of a sapphire glass lens. A complete laser wavefront is spatially divided into many tiny parts, and each part is focused on the focal plane by a corresponding small lens, and the light spots are overlapped to achieve uniform light in a specific area. The sapphire glass lens is applied to the deep ultraviolet LED inorganic module packaging device to reduce the total reflection loss between the deep ultraviolet LED package optical window-air interface, and focus the light passing through the lens on the focal plane, while increasing the emission of light Coupling ability, uniform light intensity of ultraviolet LED.