Ivan Martinovic | Polar Light Technologies: Can angled quantum wells double the recombination efficiency in gallium nitride microLEDs?
00:06:17 - 00:08:13
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Can angled quantum wells double the recombination efficiency in gallium nitride microLEDs?
In gallium nitride (GaN) based microLEDs, spontaneous and piezoelectric polarization fields generate strong internal electric fields along the polar c-axis. These fields spatially separate electron and hole wave functions within the active quantum wells, drastically reducing radiative recombination rates. This phenomenon, known as the Quantum Confined Stark Effect (QCSE), fundamentally limits internal quantum efficiency.
To overcome this physical bottleneck, Polar Light Technologies leverages a bottom-up selective area epitaxy approach to grow hexagonal pyramid microLED structures. By depositing the InGaN/GaN quantum wells along semi-polar crystal facets at an angle to the polarization field, the internal electric field is cut in half. This architectural shift dramatically increases the electron-hole wave function overlap and restores radiative recombination efficiency.
Furthermore, mitigating the QCSE through angled facet growth offers unique device-design flexibility. It allows engineers to design thicker quantum wells without suffering from carrier escape or severe wave function separation, which is typically used to manage polarization fields. The resulting device architecture achieves high radiative recombination rates and stable emission profiles, paving the way for ultra-bright microLED displays.
In this short video, you can learn:
* How the spontaneous piezoelectric polarization field in GaN limits quantum efficiency.
* The physical mechanism behind the Quantum Confined Stark Effect (QCSE) and its impact on wave function overlap.
* How growing quantum wells on angled facets halves polarization field effects and enables thicker well designs.
📋 **Clip Abstract** This clip explains how the spontaneous piezoelectric field in gallium nitride's polar direction compromises microLED quantum efficiency. By growing quantum wells at an angle, Polar Light Technologies halves the Stark effect, allowing for thicker wells and higher efficiency.
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#QuantumConfinedStarkEffect, #SemiPolarGaN, #SelectiveAreaEpitaxy, #InGaNQuantumWells, #MicroLEDDisplays, #ARDisplays
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00:08:18 - 00:10:15
Why is high microLED efficiency useless if your optical waveguide cannot capture the emitted photons?
Why is high microLED efficiency useless if your optical waveguide cannot capture the emitted photons?
Developing efficient light engines for augmented reality waveguides requires looking beyond raw internal quantum efficiency. For optical AR systems, system-level efficiency is governed exclusively by "useful photons"—those emitted within the narrow acceptance cone of the waveguide's in-coupling optics. Photons emitted at wide angles simply scatter within the light engine, causing optical crosstalk and reducing image contrast.
Traditional microLEDs based on planar platelet architectures suffer from broad Lambertian emission profiles, making it extremely difficult for external collimation optics to collect light efficiently. Similarly, utilizing down-conversion materials like colloidal quantum dots presents optical routing challenges. Because quantum dots naturally exhibit isotropic, uniform light emission patterns, they complicate the directional routing required for high-efficiency waveguide coupling.
Consequently, light engine design must prioritize directional emission directly at the emitter level. Achieving highly collimated, narrow-angle output from the microLED structure itself reduces the complexity of micro-optics and maximizes coupling efficiency. This system-centric approach is vital for minimizing battery requirements and realizing sleek, consumer-grade AR glasses.
In this short video, you can learn:
* The critical optical distinction between "useful" and "non-useful" photons in waveguide coupling.
* Why traditional flat microLED architectures fail to efficiently couple light into AR projection optics.
* Why isotropic emission from quantum dot color conversion limits its suitability for optical AR systems.
📋 **Clip Abstract** This clip addresses the critical distinction between internal quantum efficiency and usable system efficiency for augmented reality waveguides. It outlines why traditional platelet architectures and isotropic quantum dot color conversion fail to match the directional requirements of AR projectors.
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#WaveguideCoupling, #CollimatedMicroLEDs, #QuantumDotColorConversion, #LambertianEmission, #AugmentedRealityDisplays, #MicroLEDDisplays
00:10:57 - 00:12:57
Why does conventional top-down plasma etching destroy the efficiency of sub-micron microLEDs?
Why does conventional top-down plasma etching destroy the efficiency of sub-micron microLEDs?
Shrinking microLED dimensions to micron and sub-micron scales is essential for lowering manufacturing costs and fitting ultra-high-resolution displays into AR light engines. However, conventional top-down fabrication processes rely on reactive ion etching (RIE) to singulate individual dies from planar epiwafers. This mechanical and chemical processing introduces severe crystal defects along the exposed sidewalls of the active quantum wells.
As the device size decreases, the ratio of damaged sidewall perimeter to active emissive area increases exponentially. These surface defects act as non-radiative recombination centers, accelerating Shockley-Read-Hall (SRH) recombination and causing the device's External Quantum Efficiency (EQE) to collapse. At the sub-micron scale, these sidewall losses become the dominating factor governing microLED performance.
A bottom-up epitaxy approach sidesteps this fundamental material limitation by growing individual pyramidal microLED crystals atom-by-atom. Because the natural facets of the crystals define the shape of the emitter, no post-growth sidewall etching is required. This size-agnostic manufacturing strategy preserves pristine crystal boundaries and delivers high-efficiency sub-micron microLEDs.
In this short video, you can learn:
* Why scaling down microLEDs via traditional top-down etching causes severe sidewall defects.
* How the scaling ratio between damaged sidewall perimeter and active quantum well area crashes emitter efficiency.
* How a bottom-up, atomic-scale pyramidal growth method eliminates post-process etching to preserve high efficiency.
📋 **Clip Abstract** This clip highlights the severe performance degradation in traditional microLEDs caused by top-down etching defects as die sizes shrink to the micron level. It details how a bottom-up, atomic-scale pyramidal growth method eliminates post-process etching to preserve high efficiency.
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#BottomUpEpitaxy, #SidewallDefects, #SubMicronMicroLEDs, #ReactiveIonEtching, #ARLightEngines, #MicroLEDDisplays