They shine from clocks and traffic lights; they blink on our car dashboards. They flash on the soles of children's running shoes; they glow from the coffeemakers in our kitchens. They tell us that our modems are connecting to our networks; they reassure us that our cellphones are on. They lit up the face of the first personal computer and the first wristwatch with an electronic display; they illuminate today's suspension bridges and video billboards.
These tiny semiconductor sandwiches known as light-emitting diodes (LEDs) can now create every color of the rainbow and more. But LEDs all trace their genealogies back to the first visible laser diode—and it was red. The father of that primordial visible diode is Nick Holonyak Jr., the winner of this year's IEEE Medal of Honor.
Summer of '62
It all started in the summer of 1962, when a rock group called The Beatles was signing its first record contract and an astronaut named John Glenn was basking in the glory of his orbital spaceflight. Holonyak, who is now the John Bardeen Endowed Chair Professor of Electrical and Computer Engineering and Physics at the University of Illinois at Urbana-Champaign, was a 34-year-old consulting scientist at General Electric Co.'s laboratory in Syracuse, N.Y. He was fashioning simple devices of germanium and silicon, and investigating the family of so-called III-V materials, such as the semiconductor gallium arsenide.
That July, Holonyak attended the Solid State Device Research Conference in Durham, N.H. Researchers from the Massachusetts Institute of Technology's Lincoln Laboratory (Lexington, Mass.) and RCA Laboratories (Princeton, N.J.) reported there that a device based on a junction between two forms of gallium arsenide could emit photons of infrared light efficiently. This junction brought together two forms of the semiconductor, known as n-type and p-type. In the n-type region, electrons outnumber electron deficiencies, called holes; in the p-type region, the reverse is true. When single crystals of the two types are placed in direct contact with each other, a junction forms at their boundary that permits electrons and holes driven by a current to intermix and emit photons.
Holonyak and some colleagues immediately thought a step further. He explains: "We were saying, 'Wow, what will it take to make this thing coherent?' In other words, what will it take to make this into a laser?"
Holonyak went back to his General Electric lab and began to work exclusively on this question, with the aid of one full-time technician and some additional part-time help. This group was not the only one taking on the challenge. Teams led by Robert Hall, who worked in another division of GE, the Corporate Research and Development Center (Schenectady, N.Y.); Marshall Nathan at IBM Research Laboratories (now the Thomas J. Watson Research Center), Yorktown Heights, N.Y.; and Robert Rediker at MIT's Lincoln Laboratory were also, as were others in the United States and Europe. The race was on.
Hall, Nathan, and Rediker had an early lead because they were working with off-the-shelf gallium arsenide; Holonyak was instead working with an alloy of gallium arsenide phosphide, which he had to make himself. The advantage of gallium arsenide phosphide was its larger band gap, which meant that when electrons and holes combined in the material, they would emit photons of higher energy.
That higher energy translated into higher-frequency photons. Holonyak would get red light rather than infrared light‚ so he would see his success as a burst of scarlet. A laser made of gallium arsenide, by contrast, would emit infrared light, which could be viewed only indirectly, for example, on photographic film.
But wasn't visible-light emission a small payback for the steep price of having to make the material himself? "Working that way made sense to me," Holonyak responds. Growing up poor in the small rural town of Zeigler, Ill., he "didn't have much of anything," he adds. His father was a Carpatho-Rusyn coal miner who came to the United States in the early 1900s from the mountainous region that straddles the borders of Poland, Slovakia, Hungary, and Ukraine. As a boy, Nick had a pocketknife and liked whittling. "I realized you can make what you want," he states. The lesson stuck, and he applied it to semiconductors decades later. His colleagues thought he was crazy.