AlGaInP LED Vertical Structure with Periodic Transparent Reflectors
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Solution Overview
Problem
Conventional flip-chip based AlGaInP LEDs suffer from limited light reflectivity and poor luminous efficiency due to the angle of light reflection from the reflector combination.
Innovation Solution
An AlGaInP LED with a vertical structure is developed, featuring a transparent conducting film with periodicity, through-holes filled with a total-reflection metal layer, and a permanent substrate bonded via a metal bonding layer, enhancing light reflectivity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional reflector combination is used in flip-chip based AlGaInP LEDs, then the structure is simple, but the light reflectivity is limited and luminous efficiency is poor
Solution Approach 1:
The patent employs a composite reflector structure combining transparent conducting layers (ITO, ZnO) with dielectric layers (SiO2, Si3N4) to create a multi-layered optical system. This composite approach enables enhanced light reflectivity through constructive interference of reflected waves from different interfaces, directly resolving the contradiction by achieving high luminous efficiency through material composition rather than simple geometric reflection
Solution Approach 2:
The reflector is segmented into multiple periodic layers with alternating transparent conducting and dielectric materials. Each layer contributes to the overall reflectivity through its specific optical properties, allowing the system to achieve high luminous efficiency by dividing the reflection function across multiple specialized layers rather than relying on a single conventional reflector surface
2Illumination intensity
If a transparent multilayered film with periodicity is introduced, then specular reflectivity and light-emitting efficiency are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent implements a periodic multilayered structure where transparent conducting layers and dielectric layers are repeated in a regular sequence. This periodic arrangement creates consistent optical interference patterns that enhance specular reflectivity across the emission spectrum, achieving high illumination intensity through systematic repetition rather than complex aperiodic designs
Solution Approach 2:
The patent optimizes specific parameters including layer thickness (controlling optical path difference for constructive interference), material composition (selecting ITO, ZnO for conductivity and SiO2, Si3N4 for dielectric properties), and doping concentrations to achieve the desired reflectivity enhancement while maintaining manufacturability through controlled deposition processes
3Loss of energy
If through-holes are formed in the transparent conducting film and filled with total-reflection metal layer, then light reflectivity is enhanced, but the device structure becomes more complex
Solution Approach 1:
The patent introduces a porous structure by forming through-holes in the transparent conducting film and filling them with total-reflection metal layer. This creates a hybrid structure where the periodic multilayered film provides broad-band reflectivity enhancement while the metal-filled through-holes provide localized high-reflectivity zones, achieving superior light reflectivity through structural porosity
Solution Approach 2:
The total-reflection metal layer is nested within the through-holes of the transparent conducting film, creating a hierarchical structure where the metal reflection surfaces are embedded within the periodic multilayered matrix. This nesting arrangement allows the system to combine the advantages of both transparent conducting film interference reflection and metal surface reflection without requiring separate independent structures
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 improves specular reflectivity and light-emitting efficiency, while simplifying the manufacturing process compared to conventional methods.
Implementation Method 1
a transparent conducting film with periodicity, formed on the p-type window layer, wherein the transparent conducting film includes stacked transparent conducting layers and transparent dielectric layers
Implementation Method 2
a total-reflection metal layer, formed on the transparent conducting film, wherein the total-reflection metal layer fills up the through-holes
Data Source
AI summary
A method for manufacturing the AlGaInP LED having a vertical structure is provided, including: growing, epitaxially, a buffer layer, an n-type contact layer, an n-type textured layer, a confined layer, an active layer, a p-type confined layer and a p-type window layer in that order on a temporary substrate, to form a texturable epitaxial layer; forming a transparent conducting film with periodicity on the p-type window layer of the epitaxial layer, forming a regulated through-hole on the transparent conducting film, and filling the through-hole with a conducting material; forming a total-reflection metal layer on the transparent conducting film; bonding a permanent substrate with the texturable epitaxial layer via a bonding layer, and bring the total-reflection metal layer into contact with the bonding layer; removing the temporary substrate and the buffer layer; forming an n-type extension electrode on the exposed n-type contact layer; removing the n-type contact layer, and forming a pad on the n-type textured layer; and forming a p-type electrode on a back of the permanent substrate. The transparent multilayered film with periodicity provides a greater reflectivity difference and hence brings better results than the conventional reflector consisting of single-layered, or, non-periodic, transparent films; and light-emitting efficiency is enhanced.