Light-Emitting Device Intermediate Layer Refractive Index
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Solution Overview
Problem
The challenge in improving the light-emitting efficiency of light-emitting devices with a flip-chip package structure, where light is emitted towards the substrate, has not been effectively addressed.
Innovation Solution
A method involving a light-emitting device structure that includes a first semiconductor layer bonded to an intermediate layer with a refractive index between the substrate and the semiconductor layer, along with a transparent bonding layer, which reduces total light reflection and enhances light extraction through a patterned substrate and reflective layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light is emitted toward the substrate in a flip-chip package structure, then the device structure is compact and mounting is simplified, but light-emitting efficiency is reduced due to total internal reflection at the substrate-semiconductor interface
Solution Approach 1:
An intermediate layer with refractive index between 1.4 and 2.6 is introduced at the interface between the substrate and the light-emitting stack. This intermediate layer acts as an optical mediator that reduces total internal reflection by providing a gradual refractive index transition, thereby improving light extraction efficiency while maintaining the flip-chip package structure's manufacturing advantages
Solution Approach 2:
The refractive index parameter of the intermediate layer is specifically optimized to fall between 1.4 and 2.6, which is between the refractive index of the substrate (typically around 1.5-1.7) and the light-emitting stack (typically around 2.0-2.5). This parameter optimization enables effective reduction of total internal reflection without compromising the compact flip-chip structure
2Stability of the object's composition
If a high refractive index material is used for the substrate, then optical confinement is improved, but light extraction is reduced due to increased total internal reflection
Solution Approach 1:
The intermediate layer serves as an optical intermediary that bridges the substrate and the light-emitting stack. By having a refractive index that is higher than the substrate but lower than the light-emitting stack, it maintains optical confinement near the light source while facilitating light extraction into the substrate, thus resolving the contradiction between optical confinement and light extraction
3Stability of the object's composition
If the refractive index mismatch between substrate and semiconductor layer is large, then optical confinement is enhanced, but total internal reflection increases reducing light emission
Solution Approach 1:
The intermediate layer with refractive index between 1.4 and 2.6 acts as a mediator that reduces the refractive index mismatch between the substrate and the light-emitting stack. This gradual transition reduces total internal reflection at the interface while maintaining adequate optical confinement, thereby eliminating the harmful effect of excessive total internal reflection
Solution Approach 2:
By introducing an intermediate layer with a specifically optimized refractive index parameter (1.4-2.6), the abrupt refractive index change at the substrate-semiconductor interface is replaced with a gradual transition. This parameter optimization reduces total internal reflection while preserving optical confinement properties
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 approach attenuates total internal reflections and improves light-emitting efficiency by optimizing the refractive index gradient and using reflective and scattering structures to facilitate better light escape and distribution.
Implementation Method 1
how to improve the light-emitting efficiency of the light-emitting device is still an important issue in this art
Implementation Method 2
forming an intermediate layer on the second substrate, wherein a refractive index of the intermediate layer is between a refractive index of the second substrate and a refractive index of the first semiconductor layer
Data Source
AI summary
The present disclosure provides a method for making a light-emitting device. The method includes steps of providing a first substrate; forming a first semiconductor layer on the first substrate; providing a second substrate; forming an intermediate layer on the second substrate, wherein a refractive index of the intermediate layer is between a refractive index of the second substrate and a refractive index of the first semiconductor layer; and bonding the first semiconductor layer and the intermediate layer.