<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Chris M.:
I think that refers to a Pink LED they had for a short while. But, after Craig`s brief testing that made the por quality organic pink dye in the phosohor degrade badly, they discontinued them<HR></BLOCKQUOTE>
ETG is offering a pink and a lavender phosphor LED that uses a stable inorganic phosphor that should keep the LED reasonably close to its starting color through the 10,000 hour mark. Brightness will probably fall off, but the color shouldn't fade like it did with those Roithner pink lEDs.
Purple LEDs won't simply stop working; it's a slow burn all the way to the bottom that starts the monent you turn one on. The high-energy photons initiate a cascade reaction that involves dissociation (breaking apart) of atomic bonds in the quantum GaN lattice. This process occurs at the subatomic level, and at present, nothing can be done to stop it.
In simpler terms, the rude little photons of UV light smack the GaN molecules in the puss so hard, it knocks their little blocks off and effectively kills them. Once the atoms have been dissociated (ripped apart) in this manner, they are unable to recombine into GaN within the existing bandgap. It's a cumulative process which is irreversible.
The end result is the LED very slowly dims, losing the shortwave (violet) output more quickly; so after x number of hours, you're left with a dim, reddish, brownish, or purplish white LED. The whitish color stems from the existing broadband emission produced by lower energy bandgaps that exist as a result of crystalline defects already in the P-N junction, and shows up even in brand new violet LEDs.
In this final "white dwarf" state, the LED might still be bright enough to use as a pilot light on some instrument kept in a dark room, but not usable for much of anything else. Send it to the big dumpster in the sky and replace it.