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Technology

Pyramidal MicroLEDs, grown bottom-up

Our MicroLEDs are hexagonal InGaN/GaN pyramids grown bottom-up from the epi-wafer instead of being etched out of a planar epi stack, top-down. This gives excellent surfaces without etching damage, crucial for optoelectronic performance, in particular as dimensions shrink.

Technical characteristics

What bottom-up growth gives

ArchitectureHexagonal GaN pyramids with InGaN quantum wells as the active light-emitting region, grown bottom-up instead of etched out of a planar epi stack
SizePyramidal nanoLEDs demonstrated down to 450 nm
Position, density and shapeDeterministic, defined by the growth mask
SurfaceExcellent surface smoothness due to the bottom-up growth. No etching damage on the sidewalls
StrainThe geometry of the pyramids results in less strain, which increases the ability to get more indium into the quantum wells, i.e. of increasing importance with longer wavelengths
Piezoelectric fieldReduced effect, due to the pyramid base angle, meaning faster recombination time and more photons per time unit (i.e., higher data bandwidth)
Emitting areaThe emitting facet area is more than double, 113% larger, than the pyramidal base area (7.38 µm² against 3.46 µm²)
Light lobeLambertian
IntegrationFlip-chip integration proven
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Grown, not etched

Two ways to make a MicroLED

Pyramidal, next-generation MicroLEDs: pyramids grow in place with light-emitting layers on smooth, sloped facets
Conventional, first generation MicroLEDs: etching defines each MicroLED and damages its edges

Development

What has been shown, and when

  1. First blue and green pyramidal MicroLEDs

  2. Red in the same InGaN/GaN material system

  3. First working pyramidal MicroLED based display

  4. First working blue and green pyramidal MicroLED based display

  5. NanoLEDs with size of 450 nm demonstrated

    Demonstrated on the same architecture. Not today’s offering.

  6. First MicroLEDs on a manufacturing pilot line

    Produced at VTT Technical Research Centre of Finland.

Scanning electron microscope image of pyramidal MicroLEDs
Scanning electron microscope (SEM) image of pyramidal MicroLEDs.
450 nm MicroLEDs lighting up
450 nm MicroLEDs

Publications

Pyramidal GaN research

Ten peer-reviewed papers, 2011 to 2022, from the Linköping University research the company grew out of.

  2. GaN-based pyramidal quantum structures for micro-size light-emitting diode applications

    Son Phuong Le, Chih-Wei Hsu, Ivan Martinovic, Per-Olof Holtz

  3. Polarized single photon emission and photon bunching from an InGaN quantum dot on a GaN micropyramid

    Tomas Jemsson, Houssaine Machhadani, Per-Olof Holtz, K Fredrik Karlsson

  4. Direct generation of linearly polarized photon emission with designated orientations from site-controlled InGaN quantum dots

    Anders Lundskog, Chih-Wei Hsu, K Fredrik Karlsson, Supaluck Amloy, Daniel Nilsson, Urban Forsberg, Per Olof Holtz, Erik Janzén

  5. Linearly polarized single photon antibunching from a site-controlled InGaN quantum dot

    Tomas Jemsson, Houssaine Machhadani, Per-Olof Holtz, K Fredrik Karlsson, Chih-Wei Hsu

  6. Deterministic Single InGaN Quantum Dots grown on GaN Micro-Pyramid Arrays

    Per Olof Holtz, Chih Wei Hsu, Anders Lundskog, K. Fredrik Karlsson, Urban Forsberg, Erik Janzén

  7. Morphology Control of Hot-Wall MOCVD Selective Area Grown Hexagonal GaN Pyramids

    Anders Lundskog, Urban Forsberg, Per Olof Holtz, Erik Janzén

  8. InGaN quantum dot formation mechanism on hexagonal GaN/InGaN/GaN pyramids

    A Lundskog, J Palisaitis, C W Hsu, M Eriksson, K F Karlsson, L Hultman, P O Å Persson, U Forsberg, P O Holtz, E Janzén

  9. Controlled growth of hexagonal GaN pyramids by hot-wall MOCVD

    Anders Lundskog, C.W. Hsu, D. Nilsson, K.F. Karlsson, U. Forsberg, P.O. Holtz, E. Janzén

  10. Single Excitons in InGaN Quantum Dots on GaN Pyramid Arrays

    Chih-Wei Hsu, Anders Lundskog, K. Fredrik Karlsson, Urban Forsberg, Erik Janzen, Per Olof Holtz

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