Dielectric Reflector for Vertical LED Light Extraction
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Solution Overview
Problem
Conventional metal reflection films in semiconductor light-emitting devices, such as LEDs, suffer from low refractive index and excessive leakage current, leading to reduced light-emitting efficiency, especially for blue light emission from quantum well layers in nanorod structures.
Innovation Solution
A light-emitting device with an omnidirectional dielectric reflector composed of pairs of dielectric layers with different refractive indices, such as titanium oxide and silicon oxide, is used to improve light extraction efficiency and restrict leakage current by filling the space between vertical light-emitting structures without the need for additional insulation layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metal reflection film is formed to improve light extraction efficiency, then the refractive index is improved, but leakage current increases excessively
Solution Approach 1:
The patent uses a composite dielectric reflector structure consisting of multiple dielectric layers with different refractive indices (e.g., TiO2 and SiO2 layers) to replace the single-material metal reflection film. This composite structure achieves both high light extraction efficiency through optimized refractive index matching and effective leakage current blocking through the inherent insulating properties of dielectric materials.
Solution Approach 2:
The patent changes the refractive index parameter by using dielectric materials with higher refractive indices than metal films, and optimizes the thickness and arrangement of each dielectric layer to achieve maximum light extraction efficiency while maintaining electrical insulation properties that prevent leakage current.
2Illumination intensity
If a metal reflection film is used to reflect light, then light extraction efficiency is improved, but light-emitting efficiency is reduced due to excessive leakage current
Solution Approach 1:
The composite dielectric layer structure replaces metal reflection films to eliminate the trade-off between light extraction and energy loss. The dielectric materials provide both optical benefits (high refractive index for improved extraction) and electrical benefits (insulation to prevent leakage current and energy loss).
Solution Approach 2:
The dielectric reflector acts as an intermediary between the light-emitting quantum well layer and the external environment, providing both optical coupling (through refractive index management) and electrical isolation (through insulating properties), thereby preventing energy loss while maintaining high light extraction efficiency.
3Ease of manufacture
If conventional metal reflection films are used, then manufacturing is simple, but light extraction efficiency is limited due to low refractive index
Solution Approach 1:
The patent employs a composite dielectric layer structure with multiple materials (such as TiO2 and SiO2) having different refractive indices. This composite approach achieves superior light extraction efficiency through optimized optical impedance matching while maintaining compatibility with conventional semiconductor manufacturing processes like atomic layer deposition (ALD) or chemical vapor deposition (CVD).
Solution Approach 2:
The reflector is segmented into multiple thin dielectric layers with alternating refractive indices, where each layer has a specific thickness (e.g., 10-50 nm) and material composition. This segmentation creates a distributed Bragg reflector structure that enhances light extraction efficiency through constructive interference of reflected waves at each interface.
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 dielectric reflector enhances light extraction efficiency and reduces leakage current by providing a higher refractive index than conventional metal films, effectively reflecting light and preventing current leakage, thereby improving the overall performance of the light-emitting device.
Implementation Method 1
a dielectric reflector filling a space between the plurality of vertical light-emitting structures on the current diffusion layer
Implementation Method 2
a dielectric reflector includes a plurality of pairs of dielectric layers having different refractive indices
Implementation Method 3
Semiconductor light-emitting devices such as light-emitting diodes (LEDs) or laser diode (LDs) use an electroluminescence phenomenon, that is, light is irradiated from a material (semiconductor) by application of a current or voltage
Data Source
AI summary
A light-emitting device includes a first conductive semiconductor layer formed on a substrate, a mask layer formed on the first conductive semiconductor layer and having a plurality of holes, a plurality of vertical light-emitting structures vertically grown on the first conductive semiconductor layer through the plurality of holes, a current diffusion layer surrounding the plurality of vertical light-emitting structures on the first conductive semiconductor layer, and a dielectric reflector filling a space between the plurality of vertical light-emitting structures on the current diffusion layer.