On Fri, 24 May 1996, Przemek Klosowski wrote:
> IT couldn't have been the thermal radiation: red glow would mean
> several hundred degrees C, and neither semiconductor nor bondings
> nor packaging would survive that.
>
> The red glow results from carrier recombination (LED mechanism) in
> forward-polarized substrate p-n junction. [...]

I've also seen LEDs used as photodetectors using the same concept,
but in reverse of course.  They're not the greatest, but it works
in a pinch... and they come with that handy little lens built in!

Rick Miller