Here are a few bits of LED history I've come across.
There is some anecdotal evidence to suggest GaAs IR emitting diodes were classified by the military in the late 1950s, then declassified several years later.
There is also stronger evidence that a man named Henry Round discovered that silicon carbide could be made to glow green with the application of an electric charge, and that the material was somewhat monopolar (ie. it behaved like a diode, passing current in one direction but not the other).
This occurred in 1907, and was repeated by another scientist in Russia in 1923.
The first
blue LED may have actually been invented in Russia in 1973. At this time, they were producing a greenish yellow silicon carbide LED, and supposedly had working versions in red and blue as well. General Electric also produced & sold a yellow SiC LED in the early 1970s.
The first gallium nitride LED appeared on the market in 1993. It was a greenish blue LED, about as bright as the then-new silicon carbide blue. Its most unique characteristic was that it had *NO bond wires* or reflective cup. The large flat die was simply laid upside down across the top of the leadframe and pressed into place with some kind of clamp; the glow originated from a small rectangular region of the cathode.
This LED could not be soldered to by conventional means, or else the leadframe to die interface would shatter and the LED would then fail. They were originally made to be part of a colorimeter, and were sold by LEDTronics for a short time. The wavelength was 482nm, so the first picture shows the closest rendition of its true color.
This LED had a Vf of 11.0 volts at 10mA
