He was growing crystals of gallium arsenide phosphide — GaAsP, a tweak on the gallium arsenide everyone else was using for infrared diodes — and the tweak was the whole point, because it pushed the emission up into the part of the spectrum your eye actually bothers with. Red. Dim red, at that. Syracuse, a General Electric lab, 1962, and Nick Holonyak put it in front of people and it glowed.
He said fairly early on that the ordinary light bulb was living on borrowed time, which took about forty years to come true and got him called a few things in the meantime. I don't fully follow the crystal-growing end of it, the vapour-phase business with the substrate temperatures. But I've got a drawer of tubes that ran hot enough to warm a room, so I take a quiet interest in anything that makes light without making soup.
Red LEDs got trusted in spacecraft panels years before anyone let them near a lamp socket — tiny, cold, and they don't shatter under launch vibration, which a filament bulb hates. Dim red was a feature when you're staring at an instrument panel in the dark.
That red diode and its infrared cousin ended up clipped to fingertips all over the hospital. Oxygenated and deoxygenated blood absorb the two colours differently, so the clip shines both through and compares — which means a number for blood oxygen without a needle. I used one most days and never once thought about Syracuse.