Chih-Wei Hsu | Polar Light Technologies AB: Can we bypass the Quantum Confined Stark Effect without abandoning GaN-based microLEDs?
00:07:01 - 00:08:03
Other snippets from this talk
Summary of the clip:
Can we bypass the Quantum Confined Stark Effect without abandoning GaN-based microLEDs?
Conventional polar c-plane GaN microLEDs suffer severely from the Quantum Confined Stark Effect (QCSE). Strong internal polarization-induced electric fields physically separate electrons and holes within the quantum wells, which dramatically suppresses radiative recombination rates and cripples the internal quantum efficiency of the emitter.
By growing the active InGaN layers on the semi-polar sidewalls of micro-pyramids instead of the flat c-plane, the internal electrostatic environment is radically changed. The 60-degree inclined crystal orientation naturally reduces the strength of these built-in electric fields, keeping carrier wavefunctions aligned.
Engineering calculations confirm that this semi-polar architecture slashes the negative impacts of the internal polarization fields by approximately 50%. Combined with a doubled active surface area, this physics-driven design offers a highly scalable pathway to high-efficiency microdisplays as pixel sizes shrink below the micrometer scale.
In this short video, you can learn:
* How polar c-plane GaN structures generate severe built-in electric fields that degrade internal quantum efficiency.
* The physics of semi-polar crystal facets and how a 60-degree inclination mitigates carrier separation.
* Why reducing polarization field impacts by half allows microLEDs to maintain high efficiency at sub-micron scales.
📋 **Clip Abstract** This segment highlights how semi-polar pyramidal microLED facets mitigate the severe internal electric fields associated with the Quantum Confined Stark Effect. By halving these polarization field impacts, the architecture secures high internal quantum efficiency even as pixel sizes scale down.
#QuantumConfinedStarkEffect, #SemiPolarGaN, #MicroPyramidLEDs, #InGaN, #ARMicrodisplays, #MicroLEDDisplays
This is a highlight of the presentation:
Pyramidal microLEDs in the same material system paving the way for RGB emission in micro displays
More Highlights from the same talk.
00:04:42 - 00:07:01
Why are bottom-up semi-polar pyramids rendering planar microLED etching obsolete?
Why are bottom-up semi-polar pyramids rendering planar microLED etching obsolete?
Traditional microLED manufacturing relies heavily on top-down etching of planar c-plane GaN wafers, which introduces severe sidewall damage and defects that drastically degrade internal quantum efficiency as pixel sizes shrink. To overcome this, a bottom-up selective area growth approach uses dielectrics with patterned micro-holes to selectively grow hexagonal GaN pyramids within conventional MOCVD reactors.
By shifting the active InGaN/GaN quantum well growth from the conventional polar c-plane to the semi-polar sidewall facets of these pyramids, the growth dynamics are fundamentally altered. These sidewall facets naturally tilt at a 60-degree angle relative to the substrate, eliminating the need for destructive physical or chemical etching.
Crucially, this tilted geometry yields a massive spatial advantage. A simple mathematical projection reveals that utilizing the sidewall facets of the pyramidal structures effectively doubles the available active light-emitting area compared to a flat, planar c-plane layout of the same footprint.
In this short video, you can learn:
* How bottom-up selective area MOCVD growth bypasses the sidewall defect damage typical of top-down plasma etching.
* The structural mechanics of depositing InGaN active layers on the 60-degree tilted semi-polar facets of GaN pyramids.
* Why the pyramidal architecture inherently doubles the active emission area over conventional flat c-plane configurations.
📋 **Clip Abstract** Chih-Wei Hsu introduces Polar Light Technologies' bottom-up MOCVD approach for growing pyramidal microLEDs. By leveraging 60-degree tilted semi-polar sidewalls, this architecture doubles the active emitting area while completely avoiding the damaging etching processes of planar designs.
#SelectiveAreaEpitaxy, #SemiPolarGaN, #PyramidalMicroLEDs, #MOCVD, #MicroLEDDisplays, #AugmentedRealityDisplays
00:09:10 - 00:10:12
How can microLED geometry naturally beam-shape light without external micro-optics?
How can microLED geometry naturally beam-shape light without external micro-optics?
Planar microLEDs are notorious for poor light extraction due to total internal reflection within high-refractive-index GaN, which typically forces light out in a highly divergent, Lambertian emission profile. This wide-angle divergence leads to massive optical losses and optical crosstalk in high-resolution augmented reality displays.
The unique three-dimensional geometry of pyramidal microLEDs provides an inherent, self-assembling optical cavity. Thanks to the natural waveguiding and confinement properties of the hexagonal pyramid shape, the light is redirected downward through the base of the structure rather than scattering laterally.
Empirical optical measurements reveal that this geometric confinement produces a highly directional, sub-Lambertian emission profile. Remarkably, 58% of the electroluminescence is concentrated within a narrow ±20-degree cone, maximizing forward light extraction efficiency without requiring bulky external microlenses.
In this short video, you can learn:
* The structural limitations of planar LEDs that cause massive photon loss and highly divergent Lambertian emission.
* How the 3D hexagonal pyramid geometry acts as a natural waveguide to focus light output.
* The empirical proof showing 58% of emitted light confined within a narrow ±20-degree cone for high directional efficiency.
📋 **Clip Abstract** Chih-Wei Hsu explains how the natural geometric confinement of pyramidal microLEDs overcomes total internal reflection and Lambertian divergence. The resulting directional waveguide concentrates 58% of the emission within a ±20-degree angle, rendering external collimating micro-optics redundant.
#PyramidalMicroLEDs, #SubLambertianEmission, #GeometricBeamShaping, #LightExtractionEfficiency, #MicroLEDDisplays, #ARLightEngines