In 1962, 50 years ago today, Nick Holonyak Jr. and his team at GE invented the Light Emitting Diode. While LED lights are almost everywhere today — from bridges to headlights to keychain flashlights that are brighter than the sun — their initial development was ripe with uncertainty and competitive research. A direct result of another groundbreaking technology of its day, the laser, LEDs have continued to evolve and now illuminate our homes and transmit our data.
Wired Design caught up with Holonyak, now a professor at the University of Illinois, to ask him about the history, and future, of LEDs.
Wired: What was initial reception of the LED like?
Nick Holonyak: I had beaten the world to a visible laser with my alloy when I realized I’m also on the path to an LED. An editor from Reader’s Digest called me, and in February 1963 pointed at the fact that LEDs will eventually cover the whole spectrum and will be the source of white light.
And that’s what’s happened. But I thought it would happen much quicker than 50 years.
Holonyak: There was a lot of speculation that maybe light couldn’t be made coherent, like a microwave signal, or, that if it were coherent, you couldn’t even see it because the human eye had always seen incoherent light.
A scientist by the name of [Theodore] Maiman came up with the idea that, even though the others were dismissing ruby as a source, ruby could be used for masers [microwave amplification by stimulating emission of radiation], but no one had made it into a laser. And he succeeded. I think it was May 1960, he demonstrated a laser. He showed the first one. And all hell broke loose then.
The semiconductor was different — it did not produce light by a sharp transition. Just a very narrow lump of light came out. In 1962, Lincoln Laboratories of MIT, a group led by [Robert] Rediker said that they made a diode that emitted a lot of spontaneous light, and that they could use that diode in the infrared to send signals
When they reported that at a meeting in July, a lot of us said, is there a chance that we could make that coherent, like a laser?
Wired: How did this differ than what Maiman had done?
Holonyak: In Maiman’s laser, you had a flashlamp like you’re using in photography, you put out a big blast of white light, the white light is absorbed by the ruby rod, the rod kicks all the red chromium atoms up into a higher condition, where they relax back and operate as a laser.
Those are primary processes driving secondary processes, all these lamps that you see, the incandescent is a heat source, and the heat is making the atom jiggle and it emits some light. Hell, that’s a better heater than it is lamp.
The lasers I’m talking about are where the current goes in one terminal and out the other terminal, and in the path itself is the light generator because of the current going from minus to plus and generating the light. That is the diode laser.
Wired: How big were the original LEDs?
Holonyak: They were very small. Tiny. These things are tiny. Of course, you can make them bigger, and the world has made them bigger and all that. Where the semiconductor does what you want, the semiconductor wins, and it’s wiped out ordinary electronic things, you know.
Wired: Did it look at all like what an LED looks like today?
Holonyak: The ones you see today are on a cheap platform, they’re on something that’s been pressed out of metal, that’s been embedded in plastic, and a little crystal has been attached in there, and then the wire goes in there, and there’s two terminals and all that, and a crystal, plastic top and all that, but that’s just one form. My god, these can be made in all kinds of forms and varieties and geometries.
Wired: What’s left to do?
Holonyak: There’s a lot more to getting conditions right. We’re still searching for better ways of making the crystals, doing the chemistry, getting everything right.
I made that first alloy at General Electric. When I came back, I worked on some other semiconductor alloys, and that got better — that’s the one that you’re seeing primarily now that generates red orange and goes up to the yellow. Then other people changed to other forms of the alloys, and too it further, up into the blue. They had a harder time shifting the blue to the green. And nobody has solved the problem of getting yellow very well.
Wired: But those developments have been made their way into mainstream usage.
Holonyak: It’s beginning to take over lighting in general, from special things to all of the lighting. It’s in the hands now of the world and all the many things people can do with lamps, lights, in different forms, different colors in different kinds of things.
Wired: Now what? Will we see their use continue to grow?
Holonyak: You can look at them as just light sources, LEDs, but you can also make them in the form of lasers, and do surgery, photoactivation, all kinds of things that are specific to certain colors and all that. You can’t do stuff like that with a light bulb. It’s just like saying I’m going to put a heart pacemaker made out of vacuum tubes in someone — that’s a joke.
You can make a whole variety of things that go into medicine, that go into instruments, that go into cars, there are some car companies that are already fully to the point where all the lamps on the car are light-emitting diodes that will outlast the car, and not be replacing head lights or tail lights or indicator lights or all that
It’s not over; it’s in its infancy in some ways. It’s much more than its infancy, but it’s in its infancy in the sense that it can go a long, long way further.
Wired: Is that stuff you’re still working on?
Holonyak: No, my partner and I are doing something more. In the transistor where it all started, there’s a current which was a throwaway current, which is vital to the operation of the transistor and how it does what it does electrically, but that current can also be turned into a light emitter, and we’ve turned it into a light emitter that’s a laser signal, and now we have two forms of signals that can be part of, let’s say, a new generation of chips.
Optical information propagates better than electrical. Electrical decays when you, loses strength as you try to move it from one place to another place. An optical signal propagates much better. And it could be made into a chip. But we’re talking about something that may take 10, 20, 30, 40 years to go all the way.