Mikael Björk | Hexagem: How close is sub-micron red InGaN microLED technology to achieving double-digit external quantum efficiency?
13:20 - 15:45
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Summary of the clip:
How close is sub-micron red InGaN microLED technology to achieving double-digit external quantum efficiency?
Red-emitting microLEDs are notorious for low efficiency due to high dislocation density and severe sidewall damage from plasma etching. Hexagem's sub-micron platelets, which are only 0.8 microns at the base, offer a potential pathway out of this efficiency bottleneck. Testing on parallel arrays of 300 platelets demonstrates remarkably robust electro-luminescence profiles with clean, single-peak Gaussian emission at 650 to 660 nanometers.
The devices exhibit exceptional color purity, exceeding 97% across the entire biasing range. The emission peak remains remarkably stable up to a current density of 10 A/cm², beyond which it undergoes a manageable blue-shift of approximately 20 nanometers per decade. This stability is a direct consequence of the strain-relaxed, dislocation-free nature of the InGaN platelets.
Currently, these unencapsulated, on-substrate devices achieve an external quantum efficiency (EQE) between 2% and 3%, peaking at 200 A/cm². Crucially, the devices retain 85% of their peak EQE even at extreme current densities of 1000 A/cm², demonstrating minimal efficiency droop. With optimized light extraction and packaging, Hexagem expects these structures to scale into double-digit EQE performance.
In this short video, you can learn:
* The electro-luminescence characteristics of 0.8-micron red InGaN microLED arrays emitting at 650-660nm
* Why dislocation-free platelets show low efficiency droop, retaining 85% EQE at 1000 A/cm²
* The current performance bottleneck of light extraction and the path to double-digit EQE
📋 **Clip Abstract** This clip presents Hexagem's latest performance metrics for sub-micron red InGaN microLEDs, demonstrating 2-3% EQE on-substrate with high color purity. The low efficiency droop at high current densities underscores the high material quality of their dislocation-free platelet architecture.
#RedInGaN, #SubMicronMicroLEDs, #DislocationFreePlatelets, #EfficiencyDroop, #ARDisplays, #MicroLEDDisplays
This is a highlight of the presentation:
A Bottom-Up InGaN Technology for Ultra-High Brightness MicroLED Displays
More Highlights from the same talk.
03:02 - 04:58
Can we grow dislocation-free GaN micro-LEDs on high-defect substrates without inducing wafer bow?
Can we grow dislocation-free GaN micro-LEDs on high-defect substrates without inducing wafer bow?
Standard planar gallium nitride (GaN) LED growth on silicon or sapphire substrates suffers from severe lattice mismatch, creating threading dislocations that ruin efficiency, particularly for red emissions. Additionally, thick buffer layers add thermal strain that causes wafer bow and degrades manufacturing yield. Hexagem overcomes this with a bottom-up selective area growth (SAG) approach using a patterned silicon nitride mask with sub-200 nm nano-apertures.
During MOCVD growth of indium gallium nitride (InGaN), the tiny mask openings act as spatial filters, blocking defects from propagating from the buffer into the micro-LED platelets. This physical defect filtering yields completely dislocation-free GaN structures. Because these micro-scale truncated pyramids grow isolated rather than merging into a continuous film, they allow elastic strain relaxation and completely eliminate cumulative film stress and wafer bow.
This structural decoupling permits the direct growth of high-quality 15 percent InGaN barrier material on top of thin, low-cost GaN buffers. Since the platelets remain isolated out of the epitaxy, no post-growth dry etching or plasma processing is required. This fundamentally avoids the critical surface damage and non-radiative sidewall recombination that typically plagues micro-LEDs as they are scaled down.
In this short video, you can learn:
* How sub-200 nm mask apertures physically filter out threading dislocations from the buffer.
* The elimination of wafer bow by growing isolated micro-platelets instead of a continuous planar film.
* How avoiding post-growth plasma etching prevents sidewall damage and preserves radiative efficiency.
📋 **Clip Abstract** This clip explains how selective area growth through nanoscale mask openings filters out threading dislocations to yield defect-free InGaN platelets. By keeping the micro-platelets isolated during epitaxy, the technology relaxes strain elastically and eliminates the wafer bow typical of planar growth.
#SelectiveAreaGrowth, #DislocationFreeGaN, #ElasticStrainRelaxation, #InGaNMicroLEDs, #MicroLEDDisplays, #ARLightEngines
05:02 - 06:27
Why should micro-LED designers stick to the polar C-plane instead of non-polar or semi-polar facets?
Why should micro-LED designers stick to the polar C-plane instead of non-polar or semi-polar facets?
While many researchers target semi-polar facets to reduce the quantum-confined Stark effect, Hexagem deliberately builds its micro-LED platelets along the polar C-plane orientation. Theoretical modeling shows that the C-plane provides the largest hole confinement potential of all crystalline directions in the nitride material system. This enhanced confinement is crucial for boosting the radiative recombination rate and maximizing the internal quantum efficiency (IQE) potential.
Furthermore, growth kinetics on the C-plane provide significantly better control over indium incorporation and spatial uniformity compared to slanted semi-polar facets. On s-planes or at the intersections of different facets, local strain variations lead to uneven indium segregation. This segregation causes broad, multi-peak emission spectra and poor color purity.
By restricting quantum well growth strictly to the C-plane facet, Hexagem achieves highly uniform indium distribution. Cathodoluminescence mapping confirms a single emission peak at 650 to 660 nanometers with a narrow full width at half maximum of only 50 to 54 nanometers. This spectral uniformity is vital for achieving the high color purity required for commercial display architectures.
In this short video, you can learn:
* Why the C-plane facet offers the highest hole confinement and internal quantum efficiency potential.
* How restricting quantum well growth to a single crystallographic plane prevents indium segregation.
* The use of cathodoluminescence spectroscopy to confirm narrow, uniform red emission across individual platelets.
📋 **Clip Abstract** The clip details the strategic crystallographic choice of utilizing the C-plane facet over semi-polar facets for quantum well growth in micro-LEDs. This approach maximizes hole confinement and ensures uniform indium incorporation, which is critical for narrow-spectrum red emission.
#PolarCPlane, #IndiumSegregation, #Cathodoluminescence, #RedMicroLEDs, #MicroLEDDisplays, #GaNEpitaxy