5 ms·

Why can't we make the same light using LEDs?

mooman219 6y ago
> The band gap of the semiconductor determines the wavelength of the light created. The thing about LEDs is that their wavelength is fixed by the material. If you want a different wavelength, you generally need a different material. Designing materials is hard, which is why the blue led got the nobel prize a few years ago. > The type of material for UV LED is AlGaN, which will have a layer of aluminum grown on top of GaN on either Sapphire or SiC substrate. Aluminum as metal is conductive, but on AlGaN it is not. To get to a far UV band like 222nm, high density of aluminum needs to grow, which becomes non-conductive. You would need to compensate it with extremely high voltage current to generate really low level of wattage, let alone all the heat it generates. So there is no commercial vitality to it. That's the reason the whole industry on 222nm is on excimer light. This is a gist of some comments on: https://www.reddit.com/r/Optics/comments/fyqhht/how_are_leds_of_specific_wavelengths_designed_how/ https://www.reddit.com/r/Optics/comments/fyqhht/how_are_leds...
- reificator 6y ago
  > I didn't use the quote feature because it makes reading on phones hard. Quotes here generally look like the above, the indentation thing is meant for code and abused to show quotes.
  - mooman219 6y ago
    Thanks for the clarification, I misattributed users misusing quotes in code blocks as the method to quote a text (which causes some pain on small displays). I've edited the original comment to reflect this.
    - reificator 6y ago
      Glad to help!
- xutopia 6y ago
  Thank you for that comment! It's for quality comments like these that I come to Hacker News!
- Recursing 6y ago
  Great answer!
supernova87a 6y ago
As this gains interest in the public -- people need to start being really careful about being sold the idea where LEDs produce the useful frequencies of UV light -- but actually don't. There'll be products on Ebay, even Amazon, that tout LED UV -- but I'm sure tons of people will be suckered into buying those with the belief that they work. I believe you may even need to buy a true (for example) deuterium + quartz tube to get the frequencies discussed.

> The band gap of the semiconductor determines the wavelength of the light created. The thing about LEDs is that their wavelength is fixed by the material. If you want a different wavelength, you generally need a different material. Designing materials is hard, which is why the blue led got the nobel prize a few years ago. > The type of material for UV LED is AlGaN, which will have a layer of aluminum grown on top of GaN on either Sapphire or SiC substrate. Aluminum as metal is conductive, but on AlGaN it is not. To get to a far UV band like 222nm, high density of aluminum needs to grow, which becomes non-conductive. You would need to compensate it with extremely high voltage current to generate really low level of wattage, let alone all the heat it generates. So there is no commercial vitality to it. That's the reason the whole industry on 222nm is on excimer light. This is a gist of some comments on: https://www.reddit.com/r/Optics/comments/fyqhht/how_are_leds_of_specific_wavelengths_designed_how/ https://www.reddit.com/r/Optics/comments/fyqhht/how_are_leds...

reificator 6y ago
> I didn't use the quote feature because it makes reading on phones hard. Quotes here generally look like the above, the indentation thing is meant for code and abused to show quotes.
- mooman219 6y ago
  Thanks for the clarification, I misattributed users misusing quotes in code blocks as the method to quote a text (which causes some pain on small displays). I've edited the original comment to reflect this.
  - reificator 6y ago
    Glad to help!
xutopia 6y ago
Thank you for that comment! It's for quality comments like these that I come to Hacker News!
Recursing 6y ago
Great answer!

supernova87a 6y ago

As this gains interest in the public -- people need to start being really careful about being sold the idea where LEDs produce the useful frequencies of UV light -- but actually don't. There'll be products on Ebay, even Amazon, that tout LED UV -- but I'm sure tons of people will be suckered into buying those with the belief that they work. I believe you may even need to buy a true (for example) deuterium + quartz tube to get the frequencies discussed.