Re: [ATM] LED's and Diode Electronics

[Mark Holm <mdholm@telerama.com>]

Dominic-Luc Webb wrote:
> On Wed, 22 Jun 2005, Richard Schwartz wrote:
> 
> 
>>Has anybody heard of using LED's for light sensors?    How does that work?
> 
> 
> Actually, turning it the other way, I am not sure what is special,
> exactly, about PINs. All LEDs I have tested, admittedly, not a lot,
> have worked in reverse as photodiodes detectors. The made-for-the-purpose
> PINs usually, but not always, work better. I know PINs are not
> manufactured the same as LEDs, and this is maybe wherein the answer to
> this question is.

I know essentially nothing about PIN diodes, but, if the LED process is
a one photon process with all of the energy from one electron falling
across the band gap being turned into a single photon, then there is no
quantum mechanical reason I can think of that the reverse operation
should not work.  It is of course likely that there are side effect
tricks that can optimize the process for one direction or the other.
For example, LED's are fairly monochromatic and should have a fairly
monochromatic response in the reverse mode.  Maybe PIN's have a trick
that spreads their response spectrum.

-- 
Mark Holm
mdholm@telerama.com

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