Variable-Wavelength LED Display Using Porous III-Nitride Layers
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Solution Overview
Problem
Manufacturing multi-color LED displays is complex and costly due to the need for separate growth and transfer of red, green, and blue LEDs, which are difficult to integrate at high resolution, especially for longer wavelengths, and traditional mass transfer processes like stamp pick and place, fluidic assembly, and laser transfer have low yield and high costs.
Innovation Solution
A variable-wavelength LED with a chip-on-wafer (COW) design using InGaN materials that can emit multiple colors from a single diode structure, enabled by a porous III-nitride semiconductor region allowing continuous control of emission wavelength through power supply variation, reducing strain and improving crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high indium content is used to reduce bandgap for long-wavelength emission, then emission wavelength increases, but lattice mismatch strain increases leading to defect formation
Solution Approach 1:
The patent employs a porous GaN buffer layer with controlled porosity (30-70%) to accommodate the lattice mismatch between GaN and high-In InGaN layers. The porous structure provides strain relaxation while maintaining crystal quality, enabling high indium content (>20%) without excessive defect formation. This resolves the contradiction by allowing long-wavelength emission while preserving device reliability.
Solution Approach 2:
The patent changes the physical and chemical parameters of the buffer layer by creating a porous structure with specific porosity ranges and pore size distributions. This parameter change allows the buffer layer to dynamically adjust strain accommodation, enabling reliable growth of high-indium-content active regions for long-wavelength emission.
2Adaptability or versatility
If separate growth and transfer of red, green, and blue LEDs is performed, then multi-color display capability is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent grows all color LEDs (red, green, blue) on a single GaN substrate using the same InGaN material system and growth conditions. The universal GaN-based platform eliminates the need for separate growth processes and mass transfer operations, significantly reducing manufacturing complexity while maintaining full multi-color display capability.
Solution Approach 2:
The patent merges the growth of multiple color LEDs onto a single substrate, combining what were previously separate manufacturing processes into one integrated flow. This eliminates the mass transfer step and reduces manufacturing complexity while achieving full color display functionality.
3Adaptability or versatility
If mass transfer processes like stamp pick and place are used, then multi-color LED integration is achieved, but yield decreases and cost increases
Solution Approach 1:
The patent combines all LED colors into a single integrated growth process on one substrate, eliminating the mass transfer step entirely. This merging of processes eliminates the yield losses and cost increases associated with stamp pick and place, fluidic assembly, or laser transfer methods.
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
Enables efficient production of multi-color displays with reduced costs and improved yield by allowing a single LED to emit across a broad wavelength range, from blue to red, with precise control over emission wavelengths, overcoming lattice mismatch and strain issues.
Implementation Method 1
a porous III-nitride semiconductor region allowing continuous control of emission wavelength through power supply variation, reducing strain and improving crystal quality
Implementation Method 2
a variable-wavelength light emitting diode (LED)
Implementation Method 3
the light-emitting region comprises a light-emitting layer which emits light at a peak emission wavelength under electrical bias thereacross
Data Source
AI summary
A display device comprises a light emitting diode (LED) which includes a porous semiconductor material, wherein the device comprises a pixel comprising a plurality of subpixels each having a light-emitting layer. A first subpixel has a first light-emitting layer having a first area A1, and a second subpixel has a second light-emitting layer having a second area A2 different from the first area A1. The first subpixel is configured to emit at a first peak wavelength, and the second subpixel is configured to emit at a second peak wavelength different from the first peak wavelength. A method of controlling this display device and a method of manufacturing said display device are also provided.