LED Bragg Reflector Structure for Wide-Angle Brightness Gain
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Solution Overview
Problem
Existing LED technologies face challenges in optimizing the Distributed Bragg Reflector (DBR) mirror to enhance the brightness of light-emitting diodes (LEDs).
Innovation Solution
A light-emitting diode (LED) structure is developed, featuring a substrate, an epitaxial structure with an active layer, and a Bragg reflective layer. The Bragg reflective layer consists of alternately and repetitively arranged first and second film stacks, each containing material layers with different refractive indices, optimized to improve reflectivity across various incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional DBR mirror structure is used, then the manufacturing process is simple, but the reflectivity for light with large incident angles is insufficient
Solution Approach 1:
The Bragg reflective layer is divided into multiple film stacks (first film stack, second film stack, third film stack) with different optical thickness configurations. Each film stack contains alternating high and low refractive index layers with specific optical thickness ratios, creating segmented functional zones that collectively achieve broadband and wide-angle reflectivity enhancement
Solution Approach 2:
The patent employs composite material structures by combining multiple dielectric layers with different refractive indices (e.g., SiO2, TiO2, Nb2O5) in alternating sequences. These composite film stacks create interference effects that enhance reflectivity across different angles and wavelengths, solving the limitation of conventional single-structure DBR mirrors
2Illumination intensity
If the optical thickness of material layers is optimized for high reflectivity, then the brightness improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent systematically varies the optical thickness parameters of different material layers within each film stack. By adjusting the optical thickness ratios (e.g., first material layer optical thickness greater than second material layer optical thickness in first film stack, and vice versa in second film stack), the design achieves broadband reflectivity enhancement while providing manufacturing flexibility
Solution Approach 2:
Different film stacks are designed with locally optimized optical thickness configurations tailored to specific angular ranges. The first film stack optimizes for certain angle ranges while the second and third film stacks address other angular ranges, allowing each local region of the coating to perform its specific function for overall wide-angle reflectivity
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 LED structure significantly enhances the overall reflectivity of the Bragg reflective layer, achieving high reflectivity for light with both small and large incident angles, thereby improving the overall brightness of the LED.
Implementation Method 1
Bragg reflective layer includes a first film stack and a second film stack alternately and repetitively arranged. The first film stack and the second film stack both include a first material layer with a first refractive index and a second material layer with a second refractive index
Implementation Method 2
In the first film stack, an optical thickness of the first material layer is greater than that of the second material layer. In the second film stack, an optical thickness of the first material layer is less than that of the second material layer
Implementation Method 3
The first material layer and the second material layer are alternately stacked repeatedly, and the first refractive index is less than the second refractive index
Data Source
AI summary
A light-emitting diode and a light-emitting device are provided, relating to the field of semiconductor manufacturing, including a substrate, an epitaxial structure and a Bragg reflective layer. The Bragg reflective layer includes a first film stack and a second film stack alternately and repetitively arranged. The first film stack and the second film stack both include a first material layer with a first refractive index and a second material layer with a second refractive index, the first material layer and the second material layer are alternately stacked repeatedly, and the first refractive index is lower than the second refractive index. In the first film stack, an optical thickness of the first material layer is greater than that of the second material layer. In the second film stack, an optical thickness of the first material layer is less than that of the second material layer.