Seoul Biosys Begins Production of Rare Earth-Free White Micro LEDs

Re:Seoul Biosys Begins Production of Rare Earth-Free White M... by numpad0 on Monday November 02, 2026 @03:52AM (#50334486)

IIRC/IIUC, GaN could only deal with UV or at most deep-ish blue, for both input and output, due to bandgap or whatever quantum reasons I don't understand. To create white light from light emitted by a GaN device, it needs to be downconverted into visible range by use of either phosphorous materials or a nanoparticle resembling them that are activated by blue light and emit its own light. On most white LEDs, this is done by that yellow goop of plastic material dabbed on top of blue LEDs.

Could this be like nanostructure based? Like nanoscale etching that messes with the light, created on top of UV LEDs?

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Re:Seoul Biosys Begins Production of Rare Earth-Free White M... by adrian_b on Monday November 02, 2026 @10:03AM (#50337748)

The drawings in the article show that the yellow goop is no longer there.

If they do not use a multiple LED structure but they still have a fluorescent conversion layer, the layer must be very thin and deposited on the top surface of the LED. It could consist of "quantum dots", like in some TV panels, i.e. very small crystals which emit light of a color depending on the composition and size of the nanocrystal when illuminated with ultraviolet or blue light.

However, "quantum dot" is a term that has already been used for a long time in marketing with the intention to suggest a superior technology. If they were using this, I expect that they would have bragged about it.

So from the wording of the press release I think that a multiple LED structure is more likely than a "quantum dot" conversion layer, even if the latter would provide both a better spectrum coverage and superior aging characteristics (by avoiding a color hue shift in old LEDs).

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Re:Seoul Biosys Begins Production of Rare Earth-Free White M... by numpad0 on Monday November 02, 2026 @12:22PM (#50340185)

Looks like I was simply wrong with assumption that GaN could only emit blues and there are plenty of efforts made for green and red GaN LEDs with such methods as Eu doping as well as some InGaN and AlGaN structures. That makes it not pure GaN based, but there is no such things as undoped semiconductors anyway. I believe QDs are not usually made out of GaN and it also doesn't seem to be in line with the wordings used. Your theory of this being based on multiple LED sounds likely, yeah.

  https://compoundsemiconductor.net/article/114125/Realising_red_GaN-based_microLEDs_with_europium-doping
  https://pubs.aip.org/aip/jap/article/123/16/160901/400705/Perspective-Toward-efficient-GaN-based-red-light
  https://www.researchgate.net/figure/Color-online-a-Schematic-of-an-InGaN-based-red-LED-epitaxial-structure-b_fig1_355092457
  https://www.tytlabs.co.jp/en/english/review/rev402epdf/e402_007kato.pdf

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