Micro-LED Quality Validation

Abstract In this study, the thickness-dependent impact of atomic layer deposition (ALD) passivation on green micro-scaled-light-emitting diodes (micro-scaled-LEDs) varying sizes (40 70 m and 100 200 m) was systematically explored to mitigate sidewall defect-induced efficiency degradation. AlO layers (0-60 nm) were integrated into devices, followed by electrical, optical, aging analyses. Thinner (30 reduced reverse leakage 23% improved external quantum (EQE) 10.65% in smaller while thicker compromised light extraction due absorption. Larger devices exhibited limited EQE gains (6.54%) negligible thickness sensitivity. ABC + f(n) modeling confirmed suppressed Shockley-Read-Hall recombination enhanced radiative efficiency, offset partially Auger effects at higher carrier densities. Post-aging, passivated small retained 98.31% optical stability. The results emphasize a critical trade-off between defect losses scaled proposing dimension-specific ALD strategies for high-efficiency micro-LEDs.

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A method for inspecting micro LEDs on a growth substrate before transferring them to a display panel. The method involves forming electrodes and contacts on the micro LEDs and applying test power to them. This allows inspecting the LEDs' illumination before transferring. The contacts are made on the growth substrate and the test power is applied using probes. An image sensor captures the LED light and a control compares it to a reference to determine defects. This avoids disassembling the display after manufacturing to inspect the LEDs.

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Abstract Micro lightemitting diodes (MicroLEDs) are regarded as the core of nextgeneration display technology due to their high brightness and energy efficiency. However, reduction in size MicroLEDs has led increased manufacturing challenges exacerbated issues such sidewall emission, which hinder development highpixeldensity displays. This paper proposes a vertically stacked MicroLED design based on an Lshaped metal wall structure, aiming suppress emission enhance top light extraction efficiency (LEE). Through parameter scanning, dimensions thickness epitaxial layer optimized. Combined with inclined sidewalls reflective structure wall, optical characteristics red, green, blue analyzed using raytracing simulations. The is significantly reduced (with maximum 68.04% compared without walls), enhanced (the LEE within 90 direction for blue, red by 196.18%, 51.69%, 3.45%, respectively, walls). simulation results demonstrate potential fullcolor displays, providing new approach suppressing crosstalk improving performance.

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Full-color monolithic InGaN micro-LEDs can achieve the transfer of full-color subpixels through a single flip-chip bonding process, offering advantages such as simplified fabrication processes and reduced production costs for micro-LED display. In this paper, we demonstrate structure that utilizes pseudo-quantum well to long-wavelength red emission, which is applied micro-LEDs. Subsequently, present micro-LEDs, stack (R), green (G), blue (B) epitaxial layers tunnel junctions. The entire grown epitaxially by metal organic chemical vapor deposition. Micro-LEDs with mesa size 2020 m 2 RGB are fabricated. exhibits emission peak wavelength 650 nm at an injection current density 1 A/cm , dominant approximately 620 nm, achieving true emission. Even under 100 it still maintain over 600 nm. broad color gamut coverage their significant potential applications in

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The top-down submicron fabrication of blue-emitting light-emitting diodes on Qromis Substrate Technology substrates is reported. Light-emitting with mesa sizes as small 250 nm2 show ideal forward voltage and low leakage current density. It observed that sidewall treatment passivation methods used in micro-light-emitting (220 m) do not lead to the same level recombination suppression for ones (<1 m), evidenced by a 70% decrease peak external quantum efficiencies when are scaled from 2 m down nm. This attributed lateral carrier diffusion being comparable size, regardless recovery. results call rethinking impact sidewalls emerging fabricated (sub)micrometer-light-emitting diodes.

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Using atomic force microscopy (AFM) and scanning near-field optical (SNOM)-photoluminescence (PL) spectroscopy (SNOM-PL), we study the nanoscopic structural emission properties of a red InGaN hybrid single quantum well (SQW), consisting blue SQW. AFM images reveal presence threading-dislocation (TD)-related V-pits shallow trench defects. The defects are classified into three categories on basis their height relative to flat QW: lowered-, level-, raised-center SNOM-PL demonstrate that TDs all types exhibit low intensity, indicating they act as non-radiative recombination centers. Unlike previous studies low-In content samples, intensity in our high-In sample because In segregation. Given correlation dark positions between emissions, lower screw-type TD density at surface than n-GaN layer, should be one triggers formation Therefore, enhance external efficiency LEDs, it is crucial suppress segregation within decrease density.

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Adapter device and testing method for improving efficiency and accuracy of chip packaging testing, particularly for micro LED displays. The adapter has a connection plate with multiple testing units, each containing a slot for a micro LED, signal transmission sheet, and connector. The LEDs are bonded to the plate. An adapter plate connects to the testing plate. This allows testing multiple LEDs simultaneously. An ID code on the plate helps locate faulty LEDs. The adapter facilitates integrated testing by combining multiple steps, improves efficiency by finding defects faster, and provides convenience for handling and testing the LEDs.

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Detection panel and device to reduce defects and improve efficiency in testing microLEDs. The panel has multiple detection units with closely spaced electrodes. When an LED is illuminated, the panel detects electrical properties to check for defects. The spaced electrodes prevent contact damage to the LED electrodes. The panel is used with an optical emitter to shine light on the LED being tested. By detecting the electrical changes induced by illumination, the panel can determine if the LED has defects. This avoids the need for direct electrode contact and sequential testing.

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This study presents an optimized design of green-emitting Micro-LED structures, using numerical simulations to elucidate the pivotal role Micro-LEDs with pre-well and pre-layer configuration in alleviating polarization-related electric fields promoting energy band flattening. The simulation quantitatively demonstrates structure's effectiveness enhancing wave function overlap radiative recombination efficiency. These insights provide a robust theoretical foundation for experimentally observed enhancements external quantum efficiency, wavelength stability, high-speed modulation performance devices.

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Enabling testing, repair, and replacement of micro devices integrated into a system substrate like an emissive display. It provides methods and structures for identifying, fixing, and replacing defective micro devices in integrated systems like displays. The methods involve using temporary electrodes to bias and test floating contacts, optical sensors to measure light output, and fuses to disconnect defective devices. The structures include spare circuits, repair pads, and defect mapping blocks for populating and connecting replacements.

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Repairing techniques for micro LED displays to increase yield and reduce cost when defective micro LEDs are found after transfer to the system substrate. The techniques include replacing defective micro LEDs with spare ones, converting color of spares to match defects, mapping spare locations, and spatial coordinate variation to mitigate visual artifacts. It also involves calibration to correct for spatial non-uniformity induced by repair techniques.

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Transferring microdevices like LEDs from a donor substrate to a receiver substrate in a way that avoids defects and performance issues. The technique involves arranging the microdevices in cartridges, aligning the cartridges with a template, bonding them, then transferring the devices from the template to the receiver substrate. This allows selective transfer of defect-free devices from cartridges rather than transferring entire blocks from the donor substrate. The cartridges can also have anchors to hold the devices during transfer and vias for temperature and mechanical property adjustment. By testing the cartridges and adjusting transfers based on defect data, it reduces defects in the final receiver substrate.

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Micro-LEDs are suitable as special light sources that serve small sensors and for optical communication. The most important technology these applications is Micro-LED high-precision transfer (0.5 m positional accuracy). existing has the problem of low position accuracy. This study proposes a high-position-precision method based on vibrations. A single system microgripper was designed to achieve positioning. Compared with other methods, this can be used in conjunction microscope camera Micro-LED. To test performance our proposed method, Micro-LED, length approximately 40, width 20, thickness 4 m, transferred. tested. Subsequently, 5 6 array results show 2 out 30 have deviation exceeding 3 so failure. success rate >90%. root-mean-square error 0.8 m. experimental exhibits good transfers.

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Abstract MicroLED is considered as the new generation of display with longlifetime, high contrast and brightness, splicing capability, so forth. Mass transfer bottleneck that limits manufacturing at large volume, due to factors such laserlift off, pickup, metal bonding. Metal bonding between chip substrate one most important lightup yield. To solve key thermal mismatch issue backplane donor during heating, laserassisted process could be a viable solution. We present study in metallic element Au/Sn productivity, capability low cost, well good electrical conductivity, excellent strength, sensitivity surface roughness. The result presented 62 78 pixels fullcolor display, reliable connection microscale LED devices can achieved under 250C without any damage backplane. In conclusion, micromorphology formation mechanism different alloy phase compositions welded elements have been thoroughly studied, feasible technological methodology has developed for upcoming mass production modules.

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MicroLED display technology with improved yield and production efficiency by selectively removing defective microLEDs before transfer to the final substrate. The method involves testing the microLEDs on a temporary substrate, removing any failures, and then transferring the remaining good microLEDs to the permanent display substrate. This prevents filling gaps with extra microLEDs, which can have lower yield. The key is controlling the transfer and removal rates so more defective microLEDs are removed than replaced.

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Micro light-emitting diode (Micro-LED) is widely regarded as a highly promising technology in the current display field due to its excellent performance, but core issue hindering further development of Micro-LED how achieve high-precision and high-yield transfer. In this study, laser-induced forward transfer (LIFT) adopted main technique, novel blister-type dynamic release layer (DRL) material selected, characterized by gentle process minimal residue on chip after Chip-on-wafer (COW) structure that fabricates large number Micro-LEDs (15 30 m2) sapphire substrate. The COW-on-head (COH) bonding method can control uniformity overall height before within 3.5%, which favorable for subsequent stable Based analysis close relationship between gap laser energy density, study successfully achieved red/green/blue (R/G/B) chips (6400, respectively) onto corresponding chip-on-carrier 2 (COC-2), all them have one-step yield over 99.3% an average offset m or less. It worth mentioning mentioned paper different from testing repairing chips. fully reflect quality. order verify validity 1 in., f... Read More

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Abstract Microlight emitting diode (LED) based LED on silicon (LEDoS) is a promising candidate for nextgeneration AR and VR displays due to superior pixel performance potential high resolution. Traditional RGB pixels are placed single plane, which limits the To overcome this, vertically stacked using heterogeneous monolithic 3D integration (M3D) have been explored. However, previously reported vertical LED not considered heat dissipation capability of pixels, indeed important in future micro displays, utilized materials incompatible with standard CMOS processes, further limiting their practicality LEDoS. The critical regions constraint, bonding medium, typically organic polymer materials. Therefore, handle issue, fullcolor LEDs demonstrated oxide (SiO 2 ) yttrium (Y O 3 ), as mediums. These CMOScompatible offer thermal conductivity at least 10 times higher than conventional polymers. InGaN/GaN blue bonded oxides show improved management, leading external quantum efficiency (EQE) better color characteristics, including narrower full width half maximum (FWHM) purity. ... Read More

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Testing large arrays of devices like microLED displays using parallel excitation with repeated contact and interaction without damaging the probes or devices. The test tool has multiple probes that can simultaneously contact multiple device contacts. Liquid metal is applied to the probe tips before contact to act as a flexible interface. When the probes touch the device contacts, oxide pinholes form in the contact layer allowing electrical connection through the liquid metal bridge. This allows repeated contact without damaging the probes or devices. The liquid metal seals when the probes lift, preventing flow onto the contacts. This enables parallel device excitation with optical monitoring without active feedback loops to maintain probe-contact alignment.

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A test system for efficiently and accurately measuring the performance of small form factor LEDs like micro-LEDs and nano-LEDs. The system uses a probe head with obliquely angled probes that can contact the tiny LEDs without blocking emitted light. It also has a movable cover over the probe slot to protect the probes when not in use. The probes measure voltage and current through the LEDs while a separate light detector captures emitted light. This allows calculating the quantum efficiency based on all three parameters.

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Determining quality of inspection data using a machine learning model that can distinguish between defective and non-defective products without requiring labeled training data for defective products. The method involves generating training data from non-defective products, learning the ML model on that, preparing a feature spectrum from a specific layer output for non-defective training data, and using that learned model and feature spectrum to determine quality of unseen inspection data. Similarity between the inspection data feature spectrum and the known feature spectrum is calculated and a threshold is used to determine if it's non-defective or defective.

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