Flip-Chip LED With Patterned Bonding Layer for Light Extraction
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Solution Overview
Problem
Existing flip-chip light-emitting diodes using AlGaInP quaternary materials for red-light and yellow-light LEDs face low external quantum efficiency due to the use of light-absorbing GaAs substrates, which restricts light extraction and bonding quality.
Innovation Solution
A flip-chip light-emitting diode chip with a patterned transparent bonding layer, featuring a high-refractivity transparent medium layer and a transparent substrate, where the bonding layer is patterned to fill recess regions and includes pyramid-shaped recess arrays to enhance light extraction and bonding strength, using materials like aluminum oxide or titanium dioxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light-absorbing GaAs substrate is used for fabricating red-light and yellow-light LEDs, then the bonding quality is good, but the light extraction efficiency is low
Solution Approach 1:
The bonding layer is segmented into a patterned structure with periodic recesses instead of a continuous layer. This segmentation allows light that would otherwise be absorbed by the GaAs substrate to escape through the recess regions, improving light extraction efficiency while maintaining bonding quality in the raised portions of the bonding layer.
Solution Approach 2:
Different regions of the bonding layer are given different functions: the raised portions maintain bonding quality with the substrate, while the recess regions are optimized for light extraction. This local differentiation allows simultaneous optimization of both bonding quality and light extraction efficiency.
2Loss of energy
If a transparent substrate is used to improve light extraction efficiency, then the external quantum efficiency improves, but the bonding quality may be compromised
Solution Approach 1:
The patterned bonding layer acts as an intermediary between the GaAs substrate and the transparent substrate. It maintains the bonding interface where needed while creating light extraction pathways where needed, mediating between the conflicting requirements of bonding quality and light extraction efficiency.
3Area of stationary object
If a continuous transparent bonding layer is used, then the bonding coverage is complete, but the light extraction efficiency is reduced due to shadow areas
Solution Approach 1:
The continuous bonding layer is segmented into raised portions and recess portions. The raised portions provide bonding coverage, while the recess portions eliminate shadow areas and enable light extraction. This segmentation resolves the contradiction between complete bonding coverage and light extraction efficiency.
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 extraction efficiency and ensures strong bonding, allowing the transparent substrate to function effectively as a light-transmitting window, enhancing the overall performance of the flip-chip LED chip.
Implementation Method 1
a transparent medium layer over the upper surface of the epitaxial laminated layer, wherein, the upper surface is provided with a grid-shaped or array-shaped recess region
Implementation Method 2
the lower surface of the n-type semiconductor layer is arranged with pyramid-shaped recess arrays, wherein, each pyramid-shaped recess is arranged in the vertical shadow area of the transparent bonding medium layer to reflect light from the vertical shadow area
Implementation Method 3
each pyramid-shaped recess is arranged in the vertical shadow area of the transparent bonding medium layer to reflect light from the vertical shadow area of the transparent bonding medium layer; as a result, light can deviate from this shadow area, thus eliminating light reflection from the transparent bonding medium layer to the inside part of the chip
Implementation Method 4
a transparent substrate connects the patterned transparent bonding medium layer to the upper surface of the transparent medium layer; the transparent substrate serves as a light-transmitting window
Data Source
AI summary
A light-emitting diode (LED) includes an epitaxial laminated layer with an upper surface and an opposing lower surface, the LED including: a first-type semiconductor layer; an active layer; and a second-type semiconductor layer. A portion of the first-type semiconductor layer and the active layer are etched to expose a portion of the second-type semiconductor layer; a first electrode and a second electrode are disposed over the lower surface of the epitaxial laminated layer; the first electrode is disposed over a surface of the first-type semiconductor layer; the second electrode is disposed over a surface of the exposed second-type semiconductor layer; a transparent medium layer over the upper surface of the epitaxial laminated layer, having a refractive index n1> 1.6; a transparent bonding medium layer over one upper surface of the transparent medium layer, having a refractive index n2<n1.