George Zhaojun Liu | SUSTech: Can GaN-on-GaN homoepitaxy eliminate the Quantum-Confined Stark Effect in ultra-small MicroLEDs?
15:10 - 16:20
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Summary of the clip:
How can we overcome the severe efficiency droop in micro-LEDs as current density scales up?
The inherent quantum-confined Stark effect (QCSE) and poor thermal management have long bottlenecked the performance of micro-LED architectures. By transitioning to a GaN-on-GaN homoepitaxial growth platform, we can effectively eliminate QCSE while drastically improving heat dissipation. This structural optimization mitigates thermal droop and stabilizes internal quantum efficiency under high-drive conditions.
Surface states and sidewall defects induced during dry etching represent another major loss mechanism, particularly as pixel dimensions shrink. Utilizing a self-aligned fabrication flow that integrates a potassium hydroxide (KOH) wet treatment successfully clears the surface depletion region. This chemical treatment, paired with atomic layer deposition (ALD) passivation, effectively repairs sandblast damage along the mesa sidewalls.
To optimize carrier injection across these treated surfaces, indium tin oxide (oxide-based ITO) is deployed as a highly efficient current spreading layer. The synergy of KOH treatment, ALD passivation, and ITO integration yields an ideality factor approaching unity across a broad device pitch. This optimization minimizes non-radiative Shockley-Read-Hall recombination, driving a substantial boost in radiative recombination efficiency.
In this short video, you can learn:
* How GaN-on-GaN devices eliminate the quantum-confined Stark effect and optimize thermal dissipation at high current densities.
* A self-aligned fabrication process combining KOH surface treatment and ALD passivation to repair dry-etching sidewall damage.
* The role of ITO current spreading layers in achieving an ideality factor close to one for micro-LEDs ranging from 3 to 100 microns.
π **Clip Abstract** The speaker discusses the optimization of micro-LED performance through the elimination of the quantum-confined Stark effect and improved heat dissipation on GaN-on-GaN devices. He details a self-aligned fabrication process utilizing KOH surface treatment, ALD passivation, and an ITO current spreading layer to repair etching damage and enhance radiative recombination.
π€ Speaker: George Zhaojun Liu
π’ Company: SUSTech
π
Event: Mini- & Micro-LED Displays 2022: Markets, Manufacturing Innovations, Applications, Promising Start-ups
π Location: TechBlick Platform |Online
π Learn more at the next TechBlick event: https://www.techblick.com
#GaNonGaNHomoepitaxy, #QuantumConfinedStarkEffect, #NonPolarGaN, #VDefectElimination, #MicroLEDDisplays, #AugmentedRealityDisplays
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07:19 - 08:16
How do you manufacture high-yield MicroLED arrays ready for monolithic CMOS integration?
How do we overcome the severe lattice mismatch and polarization bottlenecks that limit non-visible micro-LED performance on conventional silicon substrates?
Commercial micro-LED displays have successfully leveraged silicon-on-silicon substrates within the visible light spectrum. However, extending this architecture to ultraviolet (UV) and infrared (IR) wavelengths introduces severe material degradation. High indium concentrations required for infrared emission and high aluminum fractions necessary for ultraviolet emission trigger acute lattice mismatch and strong polarization effects at the heterostructure interfaces.
To mitigate these high-strain dislocations and reduce intrinsic material defects, homoepitaxial growth on homogeneous substrates has emerged as a critical manufacturing pathway. Implementing homoepitaxy minimizes the structural stresses that otherwise compromise internal quantum efficiency in non-visible optoelectronics. Advanced research in homogeneous substrate engineering is now unlocking the true efficiency potential of these specialized bandgap devices.
Beyond substrate-level defect density, luminance output remains a primary hurdle for next-generation emissive displays. Achieving the extreme brightness values demanded by large-scale outdoor signage and high-ambient television screens requires a dual focus on both epitaxial perfection and optimized light extraction. Balancing these material and optical demands is essential for scaling micro-LED technology to large-format applications.
In this short video, you can learn:
* The material limitations of using silicon substrates for non-visible micro-LEDs.
* The role of homoepitaxy in reducing dislocations and intrinsic defects.
* The critical challenge of achieving high brightness in large-scale outdoor displays.
π **Clip Abstract** The speaker contrasts commercial visible-light micro-LEDs on silicon substrates with ultraviolet and infrared devices, which suffer from lattice mismatch and polarization due to high aluminum and indium content. He proposes homoepitaxy on homogeneous substrates to reduce defects and introduces brightness as a key challenge for large-scale outdoor displays.
π€ Speaker: George Zhaojun Liu
π’ Company: SUSTech
π
Event: Mini- & Micro-LED Displays 2022: Markets, Manufacturing Innovations, Applications, Promising Start-ups
π Location: TechBlick Platform |Online
π Learn more at the next TechBlick event: https://www.techblick.com
#HybridBonding, #SidewallPassivation, #OhmicContact, #MesaIsolation, #ARMicrodisplays, #MicroLEDDisplays
11:39 - 12:43
Why does shrinking MicroLEDs to under 5 microns destroy their external quantum efficiency?
How do we mitigate efficiency droop and peak EQE shift as micro-LEDs shrink to the sub-ten-micron regime?
As micro-LED dimensions scale down from ten microns to a single micron, the devices suffer from severe efficiency droop and a pronounced shift in the peak external quantum efficiency (EQE) relative to current density. This degradation is primarily driven by high dislocation densities and material non-uniformities inherent in conventional hetero-epitaxial growth. To overcome these fundamental material limits, transitioning to a homo-epitaxial gallium nitride (GaN-on-GaN) platform is essential to drastically reduce defect density and secure ultra-high crystal quality.
Beyond substrate-level improvements, the electrical driving EQE and droop remain highly sensitive to sidewall defects introduced during micro-patterning. At ultra-small physical dimensions, the high surface-to-volume ratio exacerbates non-radiative surface recombination along the etched edges. Consequently, fabricating high-performance sub-ten-micron emitters demands highly optimized device fabrication processes specifically designed to passivate these surfaces and suppress non-radiative recombination pathways.
In this short video, you can learn:
* The impact of scaling micro-LEDs down to one micron on efficiency droop and peak EQE current density shifts.
* Why homo-epitaxial GaN-on-GaN architectures are critical for reducing dislocation density and improving material uniformity.
* The role of optimized device fabrication in suppressing non-radiative surface recombination for electrical driving.
π **Clip Abstract** The speaker discusses the severe efficiency droop and peak EQE shifts that occur when scaling micro-LEDs down to the one-micron range. To resolve these issues, he proposes using homo-epitaxial GaN-on-GaN devices to reduce dislocation density and optimizing the fabrication process to suppress non-radiative surface recombination.
π€ Speaker: George Zhaojun Liu
π’ Company: SUSTech
π
Event: Mini- & Micro-LED Displays 2022: Markets, Manufacturing Innovations, Applications, Promising Start-ups
π Location: TechBlick Platform |Online
π Learn more at the next TechBlick event: https://www.techblick.com
#MicroLEDs, #SizeDependentEfficiencyDroop, #NonRadiativeRecombination, #ExternalQuantumEfficiency, #NearEyeDisplays, #ARDisplays