Holonyak retires after 50 years in ECE
The office of Professor Nick Holonyak, Jr, inventor of the first practical visible-spectrum LED, is quiet. Papers are no longer stacked pell-mell on the desktops as students and colleagues remember (“the infinite piles,” Holonyak called them, because they never disappeared). Instead, the desks are clean and tidy, as though company is expected. But for the first period of time in fifty years as a faculty member at the university, Holonyak, who announced his retirement, effective July 31, is not planning to receive those visitors.
A consummate researcher, Holonyak has been active in his office and lab, essentially without pausing, well into his eighties, and it has been famously stated that he had at least one major innovation each decade of his career, beginning with the first visible-spectrum LED, or light-emitting diode, which he developed in 1962 while working at General Electric in Syracuse, New York. He joined the Illinois faculty the following year.
“No, I didn’t take a sabbatical,” he told Moira Gunn, the host of NPR’s Tech Nation, during the LED symposium last fall, “because I’m living the playground where I go to play—to play with an idea and see if I can make something.”
A white coffee maker sits on a two-drawer filing cabinet near his desk. Marble-printed contact paper covers the top of the cabinet, and with a chair on either side, the coffee pot has been the hub of at least one, if not more, of Holonyak's optoelectronic breakthroughs: the transistor laser, which he developed with Professor Milton Feng, whose office is just across the hall in the Micro and Nanotechnology Laboratory. “He is a true genius,” said Feng. “It’s a great pleasure to be able to talk to somebody much better than yourself.”
In 2003, Feng received national media attention when his lab announced that they’d developed the world’s fastest transistor, surpassing IBM, the previous record holder. One morning, soon after this announcement, Feng was drinking a cup of coffee with Holonyak, as they would each morning, discussing the new transistor, but Holonyak, who may have been proud of his colleague’s success, was not particularly interested in the transistor alone. Instead, he was thinking about light. With other high-speed transistors, the heat generated by the electrical current is so high that an attached cooling device is required, a heat sink. But with Feng’s device, the heat didn’t seem to be the same issue, although it too could only be operated well below room temperature. Holonyak suggested that Feng look to see if the transistor was emitting light.
After two months of testing, it was discovered that, in fact, infrared light was being emitted, and over the next year, Feng, Holonyak, and their graduate students further developed the transistor laser, so that coherent light was being produced and so that the transistor operated at room temperature (instead of refrigerated laboratory settings). “We think in the future, integrated circuits and computing will be based on the transistor laser,” said Feng.
The transistor laser will essentially do for photonic integrated circuits what the LED is doing for lighting. Both provide vast efficiencies, significantly reducing energy losses to heat in their respective systems. The once standard incandescent bulb, which the LED is bound to replace, uses about ten percent of the energy input to produce light, while the rest is wasted as the filament overheats. The LED bulb, by contrast, is about eighty percent efficient, and this is expected to improve as the bulbs continue to be developed. The transistor laser will offer the same efficiencies by using light photons to transfer information within an integrated circuit, instead of electricity, while simultaneously performing the information transfer at a much higher rate.
“These would let data flow instantaneously to and from memory chips, graphics processors, and microprocessors, supercharging weather forecasting and online banking, security checks and telesurgery, airline reservation systems and video games, just about any application,” Holonyak and Feng wrote in a 2006 IEEE Spectrum article.
Just inside Holonyak’s office doorway, near the coatrack, there is a picture of Holonyak, Feng, and two former graduate students, Richard Chan (BSEE ’01, MSEE ’02, PhD ’05) and Gabriel Walters (BSEE ’98, MSEE ’01, PhD ’03), who all share in the invention of the transistor laser. Together, the professors and Walters co-founded Quantum Electro Opto Systems (QEOS) to develop commercial applications for these new high-speed optical interconnects, the first of which, Feng has indicated, will pertain to communication transfer for USB 3.0.
Like the LED, the transistor laser will continue to improve and be developed upon. New applications will be found, and ultimately, their presence in circuit boards could affect day-to-day lives around the globe. “The useful stuff is always continuous. The useless stuff, it disappears. Right, it’s very simple,” said Feng. “If you look at the LED, since its invention in 1962, the very useful device always continues. It’s been used.”
A large, aging poster of the periodic table hangs high on one wall of Holonyak’s office, and beneath it, there is a chart that shows the evolution of the visible-spectrum LED with a representative LED displayed at each milestone achievement, starting in the bottom right corner: the red LED Holonyak developed in 1962. At the time, others had already developed infrared light-emitting diodes, using conventional semiconductor material, but Holonyak created his own alloys using gallium, arsenic, and phosphorus (GaAsP). Using that material, he was able to bring that light into the visible spectrum.
He has often said that other researchers thought he was crazy—an electrical engineer dabbling in crystal growth, which was thought to be the realm of chemists. Alloying three elements was unheard of. Yet based on his understanding of the electrical properties of the crystal structures, his wisdom prevailed and has provided the basis for all subsequent LED developments. Commercial manufacturers quickly adopted his crystal growth technique, which he had patented, and the prevailing modern method for growing crystals—metalorganic chemical vapor deposition (MOCVD), developed by Holonyak’s former graduate student, Russell Dupuis (BSEE ’70, MSEE ’71, PhD ’72), in the late 1970s—draws on that patent.
Holonyak also used the same alloy, GaAsP, to produce the first visible-spectrum semiconductor laser, proving the viability of the III-V lasers, which are made with alloys of the elements in the third and fifth columns of the periodic table. This development paved the way for the red lasers used in compact disc players and high-frequency circuits.
A decade later, Holonyak’s chart shows a brighter red LED, along with orange-red and yellow. These were developments made by Holonyak’s former graduate student, M. George Craford (MSEE ’63, PhD ’67), who was, at that point working for Monsanto Chemical Company. At the time, Monsanto, which is now known as an agricultural biotechnology corporation, was quite involved in semiconductor production and had been the first company to mass-produce Holonyak’s red LEDs.
Another important step in the development of both LEDs and semiconductor lasers came from Holonyak’s lab in 1977. That year, he advised a first-year graduate student, Edward Rezek (MSEE ’77, PhD ’80), in growing the first quantum-well lasers. The quantum well applies the principles of the double heterostructure, where two separate alloys are sandwiched together, but by using incredibly thin layers, much thinner than any used previously, quantum-sized effects were observed. Quantum wells have been used in the development of highly efficient, even brighter LEDs and lasers, and today, quantum wells are ubiquitous in lasers for fiber-optic communications, interconnects, and compact disc players, among other things
Notably, Holonyak and Rezek created their first quantum well laser using equipment worth about $2,000. At the time, the equipment being used in commercial laboratories—equipment that would have produced the same results—was worth at least $1 million. Holonyak has often credited this tenacity to his childhood, growing up in a poor, coal mining community in southern Illinois, about twenty-five miles from the Shawnee National Forest. “They were used to the idea: Your house needs repairing; you do it. You need kindling wood; you do it,” he has said.
Subsequently in 1977, Holonyak worked with Dupuis on using MOCVD to grow quantum well lasers, and this is still the dominant method of manufacturing quantum-well lasers today.
Following these innovations, the LED evolution chart shows the lights becoming even brighter, and in 1993 the first high-brightness blue LED was developed. White followed shortly thereafter. With a combination of these, almost any color can now be produced, and far from the simple device indicators, showing the charge of a laptop or camera, LEDs are used in everything from backlighting cellphone displays, to stadium scoreboards, to architectural lighting. Some cities have switched entirely to LED street lights, and in the home, LED bulbs are soon to become a norm: a form of lighting that, Holonyak has long predicted, will replace Edison’s incandescent bulb. Even the now-common CFLs are less energy efficient than LEDs.
After the quantum well laser, in 1981, Holonyak and his graduate student, Wyn Ladig (PhD ’81), introduced impurity-induced layer disordering. This selectively intermixes layers in an alloy semiconductor stack, preventing the lasers from breaking apart at the facets. This technique is now especially important in high-power lasers for underwater and space telecommunications where long-term reliability is imperative.
One of Holonyak’s former students, Donald Scifres (MSEE ’70, PhD ’72), was among the first to recognize the potential of impurity disordering for underwater communications, and he founded a semiconductor laser company, SDL, Inc., in 1983, to make that a reality. As an indication of the importance of this technique, when SDL was purchased by JDS Uniphase Corporation in 2001, at $41 billion, it was the largest technology merger ever done at that time.
Another industry-changing contribution came in 1990 when Holonyak and John Dallesasse (BSEE ’85, MSEE ’87, PhD ’91)—then a graduate student in Holonyak’s lab, now an Illinois professor—discovered that stable native oxides could be formed from and buried within certain III-V semiconductor structures, confining current and optical signals within an oxidized aperture. This technique subsequently found application in vertical-cavity surface emitting lasers (VCSEL), and today these oxide-confined VCSELs are ubiquitous in telecommunications, comprising almost all of the energy-efficient, high-speed lasers used for optical interconnects.
On a shelf above Holonyak’s computer, there is an empty champagne bottle with a hand-written inscription on the label: “Bardeen / Nobel Prize / 10-20-72,” it reads. Holonyak received his undergraduate and graduate degrees from Illinois, and the bottle was given after his graduate research advisor, Professor John Bardeen, the co-inventor of the transistor, won a second Nobel Prize in Physics in 1972. Holonyak was Bardeen’s first graduate student, completing his doctorate in 1954, and he holds the John Bardeen Endowed Chair in Electrical and Computer Engineering.
“He was more than special in my life,” Holonyak said during the LED symposium last fall. “I don’t think you would be here if Bardeen hadn’t been Bardeen and if the transistor didn’t happen the way that it happened.”
Bardeen himself, as a graduate student at Princeton University, studied under Eugene Wigner, later a Nobel laureate in physics, and this long academic pedigree still continues. When Holonyak was presented with the National Medal of Technology by President George W. Bush in 2003, two of his previous graduate students were given the award simultaneously: Craford and Dupuis, both mentioned earlier. The academic family has also stretched into multiple generations. Professor Milton Feng (MSEE ’76, PhD ’79), who has collaborated with Holonyak on the transistor laser, was a graduate student at Illinois, working with Professor Gregory Stillman (MSEE ‘65, PhD ‘67), one of Holonyak’s early students. “Number one grandson,” Feng said proudly.
At a celebration for Holonyak’s eightieth birthday in 2008, Craford reported that the labs at Philips Lumileds Lighting Company, where the best-reported high-power white LED had been developed under his supervision as chief technical officer, still boasted “a large group of Holonyak’s students and students of Holonyak’s students.”
On Holonyak’s office wall, hanging beneath two photographs of John Bardeen, is Holonyak’s own wall of fame. There is an image of him with George H. W. Bush in 1990, when he was awarded the National Medal of Science. “To Dr. Nick Holonyak, Congratulations and Best Wishes,” Bush wrote along the margin. And there is an image of him thirteen years later, back in the White House, when President George W. Bush presented him, Craford, and Dupuis the National Medal of Technology. These are the highest honors given by U.S. presidents for scientific and technological achievement, and Holonyak is one of the few individuals to receive both.
There is an image of him in Saint Petersburg, Russia, accepting the Global Energy International Prize from Russian President Vladimir Putin in 2003—the first year the award was given—and there is an image of him at the Japan Prize ceremony in 1995, when he was awarded by Emperor Akihito. There is also an image of Holonyak speaking after receiving the Lemelson–MIT Prize in 2004.
These are but a few of the awards he has received throughout his career, and to hang photographic documentation of each on the wall would certainly require a substantial addition of surface area. Among other distinctions, Holonyak was inducted into the National Inventors Hall of Fame in 2008 and into the Consumer Electronics Association Hall of Fame in 2006. He was named a charter member of the National Academy of Inventors, and he is a member of the National Academy of Engineering and the National Academy of Sciences. He is a life member of IEEE, and in 2003, he won the IEEE Medal of Honor, the highest award given by the association. Two years before, he was recognized with the Frederic Ives Medal, the highest award granted by The Optical Society (OSA).
Even with all of these recognitions, “I find he is a very humble guy,” Feng said of Holonyak. There were many occasions where Holonyak declined awards, including honorary degrees from other institutions. “He figured: I already invented stuff and nothing’s more satisfactory than having invented the work. He always reminded me about that. It’s not for the glory; it’s whether the work is going to last.”
In addition to the mementos representing Holonyak’s long and distinguished career—the pictures, the Bardeen bottle, the coffee pot—one of the most notable aspects of his office is that, unlike many faculty offices, which are removed from the research labs and have tall windows with bosky views, Holonyak’s office has no window and the lab where he would work side by side with his graduate students is located just beyond his computer desk. There are two long workbenches and several fume hoods, on which parts and tools are arrayed. “This is where ideas are generated,” Feng said, with obvious admiration for his friend and colleague.
Even now, with Holonyak’s retirement, Feng hopes to continue working with Holonyak. “I go to see him every week, spend about one hour talking about our latest research work,” Feng said.
Last fall, at the LED symposium, Dean Andreas Cangellaris (then ECE department head), introduced Holonyak before a lunchtime conversation saying, “As we know…Nick is an amazing communicator.” Holonyak was leaning back in his chair in a pressed white shirt and a black suit jacket. “Not exactly,” he interjected with a laugh. “Not exactly.” Even with international honors earned, even with technological innovations that have impacted lives around the world, Holonyak doesn’t take himself too seriously. And it is that spirit—the humble innovator—which will be greatly missed in the research halls of Illinois.