Early History of Yellow SiC LEDs
Soviet Yellow SiC LED from the early 1970's
GE Yellow SiC LED from the late 1960's
Silicon carbide LEDs first became a significant commercial success when
Cree got them on the market in the
early 1990's. But those were not yellow, but were the first commercially
successful blue LED. Those original silicon carbide blue LEDs were notable
for being unusually tolerant of high temperatures. Craig Johnson mentions
that he put one in a modem that was since ruined by a serious lightning surge.
That LED was discolored by being partially carbonized but it still worked
afterwards and it is not dead yet!
Cree's main LED products now have silicon carbide as a substrate but gallium nitride or indium gallium nitride as active ingredients, and come in four varieties of blue as well as green and blue-green.
Now back to yellow silicon carbide LEDs:
Craig posts his evaluations and some photos of this LED in the 1970's section of his online LED Museum.
The die in this LED is a translucent light green block maybe .4 to .5 mm square by .15 to .2 mm thick. The anode contact covers the entire "lower" surface of the die. The cathode covers one side or nearly half of the "top" surface of the die.
The die glows a slightly greenish shade of yellow, as opposed to the
orangish "amber" or "sodium yellow" of most yellow LEDs. The glow was
brighter at the anode edge of the sides than elsewhere on exposed parts of
the die. The brighter parts of the glow, towards the anode, were slightly
less green than the glow from elsewhere on the die.
I suspect only a thin layer at or near the anode was glowing.
Light output was less than that of all common visible LEDs that had major commercial success.
The spectrum was a band wider than that of most yellow LEDs, extending from roughly 530 nm in the green to roughly 640 nm in the red. The overall color of the glow was about that of 575 nm, so 575 nm is the dominant wavelength. I do not know what the peak wavelength was.
I did not notice any variation with temperature. I did try operating this LED lamp immediately after chilling it in my freezer, and also at a highish current of 15 mA to warm it up a little.
Voltage drop was:
3.4 V at 3.5 mA
4.2 V at 8 mA
5 V at 15 mA
HERE IS THE DATASHEET!
Scanned and de-smudged, in Russian! Someone wrote a few notes on it. More notes added by another website fan. This datasheet apparently came with two LED lamps, shown in Craig Johnson's web site in the yellow LED section and in the 1970's portion of his online museum.
One lamp and the datasheet were loaned to me by Craig Johnson in separate instances and had to be returned.
Anyone who wants to add notes and/or translations to English are welcome to mail email@example.com!
One of my major website fans, Lee Lowry, tells me that the added handwriting is at least a majority of the English that anyone needs to know.
But I still welcome any additional comments as well as outright translations! Anyone wanting to forward translations to the Online LED Museum Curator as opposed to me, e-mail Craig Johnson at firstname.lastname@example.org.
Craig Johnson now has a page on GE yellow silicon carbide LEDs from the late 1960's here
and he recently added a similar one here on 4/1/2010.
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