Seth Coe-Sullivan | NS Nanotech: How do photonic crystal cavities simultaneously narrow emission cones, reduce spectral FWHM, and increase LED quantum efficiency?
00:13:41 - 00:15:36
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How do photonic crystal cavities simultaneously narrow emission cones, reduce spectral FWHM, and increase LED quantum efficiency?
In display optics, there is a classic trade-off between light extraction, color purity, and directionality. Standard LEDs emit light isotropically over a wide angle and broad spectrum, requiring lossy color filters and complex collimating micro-optics to couple efficiently into narrow-acceptance-angle waveguides for AR glasses.
By organizing the nanowires into a periodic lattice, they function as a photonic bandgap structure in the X-Y plane. This periodic refractive index variation creates a resonant cavity that accelerates spontaneous emission via the Purcell effect, funneling more energy into the desired optical modes before non-radiative recombination can occur.
The result is a highly directional, 10-degree emission cone and extremely narrow spectral linewidths without sacrificing efficiency. In fact, Coe-Sullivan explains that instead of losing light to achieve these properties, the accelerated emission actually increases the overall internal quantum efficiency of the device.
In this short video, you can learn:
* How a photonic crystal lattice of nanowires controls the direction and spectrum of emitted light.
* The role of the Purcell effect in accelerating spontaneous emission to beat non-radiative recombination.
* How display engineers can tune the cavity Q-factor to balance spectral width and avoid metamerism issues.
š **Clip Abstract** Seth Coe-Sullivan explains how embedding nanowire LEDs into a photonic bandgap lattice creates a resonant cavity that narrows the emission angle and spectral linewidth. This design boosts overall efficiency by accelerating spontaneous radiative emission to outrun non-radiative loss mechanisms.
#PhotonicCrystalCavity, #PurcellEffect, #NanowireLEDs, #PhotonicBandgap, #MicroLEDDisplays, #ARWaveguides
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00:07:39 - 00:08:32
Can we grow monolithic RGB MicroLEDs in a single epitaxial step without transfer or color conversion?
Can we grow monolithic RGB MicroLEDs in a single epitaxial step without transfer or color conversion?
Conventional microLED displays face major yield and cost bottlenecks due to the need to mass-transfer millions of individual red, green, and blue pixels, or rely on color conversion materials like quantum dots that degrade over time. Monolithic integration on a single substrate is the holy grail, but standard planar GaN epitaxy cannot easily achieve this due to lattice mismatch and strain constraints.
Seth Coe-Sullivan explains how NS Nanotech overcomes this bottleneck using catalyst-free selective area growth of InGaN nanowires. By simply varying the diameter of the individual nanowires during a single epitaxial run, the localized strain and indium incorporation are altered, shifting the emission wavelength across the entire visible spectrum.
This breakthrough enables the direct growth of red, green, and blue sub-micron pixels adjacent to each other on a single wafer. This process completely eliminates the need for precision physical assembly of three separate LED wafers, dramatically simplifying the supply chain for AR/VR microdisplays.
In this short video, you can learn:
* How nanowire diameter directly controls the semiconductor bandgap during MBE epitaxy.
* The mechanism behind growing multi-color RGB pixels in a single monolithic growth step.
* Why eliminating transfer assembly is a game-changer for the commercial microdisplay industry.
š **Clip Abstract** Seth Coe-Sullivan describes how tuning the physical diameter of GaN-based nanowires enables monolithic RGB pixel growth on a single substrate. This technique bypasses the costly pick-and-place transfer steps typically required to assemble high-resolution microdisplays.
#InGaNNanowires, #SelectiveAreaGrowth, #MonolithicRGB, #BandgapTuning, #MicroLEDDisplays, #ARVRMicrodisplays
00:10:36 - 00:11:55
Why do sub-micron red InGaN nanowire LEDs outperform conventional 20-micron planar microLEDs?
Why do sub-micron red InGaN nanowire LEDs outperform conventional 20-micron planar microLEDs?
Planar red microLEDs based on AlInGaP suffer from catastrophic efficiency drops when scaled down to sub-10 micron dimensions due to high sidewall recombination velocities. While InGaN is a more robust material system, incorporating enough indium for red emission introduces high strain, dislocations, and strong piezoelectric fields that ruin internal quantum efficiency.
NS Nanotech demonstrates a path forward using InGaN nanowires that naturally relax strain elastically along their sidewalls. This strain relaxation allows for higher indium incorporation without generating defects, enabling deep red emission in sub-micron structures.
Coe-Sullivan presents data showing sub-half-micron red devices achieving over 1% external quantum efficiency (EQE). This exceeds the efficiency of conventional planar microLEDs that are tens of times larger, showcasing the superior scaling properties of nanowire architectures.
In this short video, you can learn:
* Why conventional AlInGaP and planar InGaN red LEDs fail at the sub-micron scale.
* How InGaN nanowires relax strain to allow high indium concentrations for efficient red emission.
* The performance benchmarks of sub-half-micron red nanowire LEDs.
š **Clip Abstract** The speaker presents breakthrough efficiency data for sub-micron red InGaN nanowire LEDs, achieving over 1% EQE at dimensions under 0.5 microns. This performance beats conventional planar LEDs of much larger sizes by overcoming the strain limits of indium-rich GaN.
#InGaNNanowires, #RedMicroLEDs, #StrainRelaxation, #SubMicronLEDs, #MicroLEDDisplays, #ARDisplays