Transparent Substrate Transfer for AlGaInP LED Light Extraction
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Solution Overview
Problem
Conventional AlGaInP light emitting diodes (LEDs) suffer from low external quantum efficiency due to light absorption by the GaAs substrate, limiting their light emitting efficiency.
Innovation Solution
A four-element LED with a transparent substrate is developed by roughening the GaP layer of the AlGaInP-LED epitaxial wafer, bonding it with a transparent substrate such as sapphire, aluminum oxide, or glass, and removing the GaAs substrate, enhancing light extraction through refractive index matching and chemical mechanical polishing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a GaAs substrate is used in conventional AlGaInP-LED, then the LED structure is simple and easy to manufacture, but the external quantum efficiency is very low due to light absorption by the GaAs substrate
Solution Approach 1:
The patent extracts and removes the problematic GaAs substrate from the LED structure. By transferring the AlGaInP epitaxial layer to a transparent substrate (such as sapphire or glass), the light-absorbing GaAs substrate is completely eliminated, allowing light to escape freely without absorption losses and significantly improving external quantum efficiency
Solution Approach 2:
The patent introduces a transparent substrate as an intermediary carrier to replace the GaAs substrate. This transparent substrate serves as a mediator that supports the AlGaInP epitaxial layer while being optically transparent, thus enabling light extraction without the harmful light absorption effects of the original GaAs substrate
2Loss of energy
If the GaP layer surface is roughened to improve light extraction, then the light extracting rate increases, but the bonding surface quality deteriorates
Solution Approach 1:
The patent segments the functional requirements by separating the light extraction function from the bonding function. The GaP layer surface is roughened to enhance light extraction, while a distinct transparent substrate provides the smooth bonding interface. This segmentation allows each surface to optimize for its specific function without compromise
Solution Approach 2:
The patent applies local quality by creating different surface characteristics in different regions. The GaP layer surface is locally roughened to improve light extraction, while the bonding interface with the transparent substrate maintains local smoothness for reliable bonding. Each region has optimized properties suited to its specific function
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 significantly increases the light extracting rate and eliminates the risk of electric leakage, resulting in improved light emitting efficiency compared to conventional LEDs.
Implementation Method 1
gained light extracting rate is designed and arranged based on the refraction index of the film material
Implementation Method 2
the surface of a GaP layer of the AlGaInP-LED epitaxial wafer is roughened and acts as a bonding surface
Data Source
AI summary
A four-element light emitting diode with a transparent substrate, comprising a AlGaInP light emitting diode (LED) epitaxial wafer, and the surface of a GaP layer of the AlGaInP-LED epitaxial wafer is roughened into a bonding surface, a film is plated on the bonding surface and is bonded with a transparent substrate, and finally a GaAs substrate is removed. The transparent bonding disclosed herein can replace the GaAs substrate made of light absorption materials with the transparent substrate by substrate transfer technology, increasing the light emitting efficiency of the light emitting diode chip and avoiding extremely low external quantum efficiency caused due to the limitations of the material of conventional AlGaInP light emitting diode and the substrate; in addition, with the support of the cut path pre-etching technology, back melting or splashing during the epitaxial layer cutting process is avoided, light emitting efficiency is increased and electric leakage risk is eliminated.