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Science And Nature

The Unsung Inventor Who Chased the LED Rainbow

Walk through half of a football fields worth of low partitions, filing cabinets, and desks. Note the curved mirrors hanging from the ceiling, the higher to see the maze of engineers, technicians, and support staff of the development laboratory. Shrug once you spot the plastic taped over some of the mirrors to obstruct that view.

Visit the heart of the labyrinth and there find M. George Craford, R&D manager for the optoelectronics division of Hewlett-Packard Co., San Jose, Calif. Sitting in his shirtsleeves at an industrial beige metal desk piled with papers, amid dented bookcases, gym bag in the corner, he will not appear to be anybodys definition of a star engineer.

Appearances are deceiving.

This short article was initially published as M. George Craford. It appeared in the February 1995 problem of IEEE Spectrum. A PDF version can be acquired on IEEE Xplore. The photographs appeared in the initial print version.

Have a look around through the next couple of days, advised Nick Holonyak Jr., the John Bardeen professor of electrical and computer engineering and physics at the University of Illinois, Urbana, and the creator of the initial LEDs. Every yellow light-emitting diode you seethats Georges work.

Holonyak sees Craford being an icebergshowing a little tip but leaving an incredible breadth and depth unseen. Indeed, Craford does end up being filled with surprisesthe gym bag, for instance. He skips lunch for workouts in HPs basement gym, he said, to obtain in form for his next adventure, whatever that could be. His latest was climbing the Grand Teton; others have ranged from parachute jumping to whitewater canoeing.

His biggest adventure, though, has been some 30 years of research into light-emitting diodes.

The decision of space

When Craford began his education for a technical career, inthe 1950s, LEDs had yet to be invented. It had been the experience of space that called to him.

The Iowa farm boy was introduced to science by Illa Podendorf, an writer of childrens science books and a family group friend who kept the young Craford given texts that suited his interests. He dabbled in astronomy and joined up with the American Association of Variable Star Observers. He built rockets. He performed chemistry experiments, onetime, he recalls with glee, generating an explosion that cracked a window in his home laboratory. Once the time came, in 1957, to choose a college and a significant, he made a decision to pursue space science, and selected the University of Iowa, in Iowa City, because space pioneer James Van Allen was a physics professor there.

Vital statistics


Magnus George Craford

Date of birth

Dec. 29, 1938


Sioux City, Iowa


185 cm


Wife, Carol; two adult sons, David and Stephen


BA in physics, University of Iowa, 1961; MS and PhD in physics, University of Illinois, 1963 and 1967

First job

Weeding soybean fields

First electronics job

Analyzing satellite data from space


About 10

People esteemed

Explorer and adventurer Sir Richard Burton, photographer Galen Rowell, Nobel Prize winner John Bardeen, LED pioneer Nick Holonyak Jr.

Latest book read

The Charm School

Favorite book

Day of the Jackal

Favorite periodicals

Scientific American, Sports Illustrated, National Geographic, Business Week

Favorite music

String quartets

Favorite composers

Mozart, Beethoven


I dont use one

Favorite Television show


Favorite food

Thai, Chinese

Favorite restaurant

Dining area at San Franciscos Ritz Carlton Hotel

Favorite movies

Bridge on the River Kwai, Butch Cassidy and the Sundance Kid, The Lion in Winter

Leisure activity

Hiking, walking, snow skiing, bicycling, tennis, and, lately, technical rock climbing.


Sable Wagon (an organization car)

Pet peeves

Individuals who work with me who dont arrived at me with little problems, which fester and become big ones.

Organizational membership

IEEE, Society for Information Display

Favorite awards

National Academy of Engineering, IEEE Fellow, IEEE Morris N. Liebmann Memorial Award; but all you do is really a team thing, therefore i have mixed feelings about awards.

Because the space race heated up, Crafords fascination with space science waned, regardless of a summer job analyzing data returned from the initial satellites. He previously learned a little about semiconductors, an emerging field, and Van Allen pointed him toward the solid-state physics program at the University of Illinois, where Craford studied first for a masters degree, a PhD.

The glowing Dewar

For his doctoral thesis, Craford began investigating tunneling effects in Josephson junctions. He previously invested many years for the reason that research when Holonyak, a pioneer in visible lasers and light-emitting diodes, left his position at General Electric Co. and joined the Illinois faculty. Craford met him at a seminar, where Holonyak was explaining his work in LEDs. Recalled Craford: He previously just a little LEDjust a red speckand he plunged it right into a Dewar of liquid nitrogen, also it lit up the complete flask with a scarlet light.

Entranced, Craford immediately spoke to his thesis adviser about switching, a reasonably unusual proposal, because it involved dropping years of work. My thesis adviser was good about any of it; he previously been spending less time round the lab lately, and Holonyak was accumulating an organization, so he was ready to take me on.

Craford believes he persuaded the laser pioneer to simply accept him, the senior man recalls things differently.

Crafords adviser was running for U.S. Congress, Holonyak said, and he explained, Ive got this good student, but Im busy with politics, and everything we do someone publishes before me. I cant take proper care of him. Id as if you to choose him up.

Nonetheless it happened, Crafords career path was finally setand the lure of the glowing red Dewar never dimmed.

Holonyak was growing gallium arsenide phosphide and deploying it successfully to obtain bright LEDs and lasers. He assigned his new advisee the work of borrowing some high-pressure equipment for experiments with the material. After getting a professor with a pressure chamber he was ready to lend, Craford create work in the basement of the materials research building. He’d carry GaAsP samples from the lab to the materials research basement, cool them in liquid nitrogen, raise the pressure to review the variation of resistivity, and see unexpected effects.

Just cooling some samples would cause the resistance to move up many times. But add pressure, plus they would rise several orders of magnitude, Craford said. We couldnt find out why.

Eventually, Craford and a co-worker, Greg Stillman, determined that variations in resistance were related not merely to pressure but additionally to light shining on the samples. Once you cooled an example and shone the light onto it, the resistance went downway downand stayed this way all night or days so long as the sample was kept at low temperature, an impact called persistent photoconductivity. Further research showed that it occurred in samples doped with sulfur however, not tellurium. Craford and Stillman each had enough material for a thesis and for a paper published in the Physical Review.

The phenomenon appeared to have little practical use, and Craford put it out of his mind, until many years later when researchers at Bell Laboratories found it in gallium aluminum arsenide. Bell Labs called it the DX Center, that was catchy, studied it intensively, and as time passes, many papers have already been published onto it by various groups, Craford said. Holonyaks groups contribution was largely forgotten.

He doesnt promote himself, Holonyak said of Craford, and sometimes this troubles me about George; Id prefer to get him to become more forward concerning the fact that he’s got done something.

Proceed to Monsanto

After receiving his PhD, Craford had several job offers. Probably the most interesting were from Bell Laboratories and the Monsanto Co. Both were focusing on LEDs, but Monsanto researchers were concentrating on gallium arsenide phosphide, Bell researchers on gallium phosphide. Monsantos research operation was less popular than Bell Labs and taking the Monsanto job appeared to be a risk. But Craford, like his heroadventurer Richard Burton, who spent years seeking the foundation of the Nilehas little resistance to choosing the less well-trodden path.

Besides, Gallium phosphide just didnt seem right, said Craford, but who knew?

In his start at Monsanto, Craford attempted both lasers and LEDs. He centered on LEDs regular when it became clear that the defects he and his group were encountering in growing GaAsP on GaAs substrates wouldn’t normally permit fabrication of competitive lasers.

[He] didnt toot their own horn. When George [Craford] published the task, he put the names of the people he previously growing crystals and putting the items together before his name.

Nick Holonyak

The breakthrough that allowed Craford and his team to exceed Holonyaks red LEDs to generate very bright orange, yellow, and green LEDs was prompted, ironically, by Bell Labs. A Bell researcher who gave a seminar at Monsanto mentioned the usage of nitrogen doping to create indirect semiconductors act similar to direct ones. Direct semiconductors are often much better than indirect for LEDs, Craford explained, however the indirect type still must be used due to band gaps wide enough to provide off light in the green, yellow, and orange area of the spectrum. The Bell researcher indicated that the labs had had considerable success with Zn-O doping of gallium phosphide plus some success with nitrogen doping of gallium phosphide. Bell Labs, however, had published early experimental work suggesting that nitrogen didn’t improve GaAsP LEDs.

Man holding panel with 6 by 3 array of LEDs over his head with both hands

Nonetheless, Craford believed in the promise of nitrogen doping as opposed to the published results. We decided that people could grow better crystal and the experiment works for all of us, he said.

A little team of individuals at Monsanto did make it happen. Today, some 25 years later, these nitrogen-doped GaAsP LEDs still form a substantial proportionsome 5-10 billionof the 20-30 billion LEDs sold annually nowadays.

The original reaction was, Wow, thats great, but our customers have become pleased with red LEDs. Who needs other colors?

George Craford

Again, Holonyak complains, Craford didnt toot their own horn. When George published the task, he put the names of the people he previously growing crystals and putting the items together before his name.

His peers, however, have recognized Craford because the creative force behind yellow LEDs, and he was recently made an associate of the National Academy of Engineering to honor this work.

Craford recalls that the brand new palette of LED colors took a while to catch on. The original reaction, he said, was, Wow, thats great, but our customers have become pleased with red LEDs. Who needs other colors?

Westward ho!

Following the LED work was published, a Monsanto reorganization bumped Craford up from the lab bench to manager of advanced technology. One of is own first tasks was to choose researchers to be let go. He recalls this among the toughest jobs of his life, but subsequently discovered that he liked management. You have significantly more variety; you have significantly more things that you will be semi-competent in, if you pay the cost of learning to be a lot less competent in virtually any a very important factor, he told IEEE Spectrum.

Soon, in 1974, he was bumped up again to technology director, and moved from Monsantos corporate headquarters in St. Louis to its electronics division headquarters in Palo Alto, Calif. Craford was in charge of research groups developing technology for three divisions in Palo Alto, St. Louis, and St. Peters, Mo. One handled compound semiconductors, another with LEDs, and the 3rd with silicon materials. He held the post until 1979.

Even while a manager, he remained a scientist to one’s teeth, said David Russell, Monsantos director of marketing during Crafords tenure as technology director. He could be a pure intellectual scientist to a fault for a vintage peddler like me.

Though always the scientist, Craford also offers a reputation for relating well to people. George will be able to express complicated technical issues in a manner that most of us can understand, said James Leising, product development manager for HPs optoelectronics division.

Leising recalled that whenever he was production engineering manager, a posture that occasionally put him incompatible with the study group, George and I were always in a position to workout the conflicts and leave friends. That wasnt always the case with others in his position. Onetime specifically, Leising recalled, Craford convinced the production band of the necessity for precise control of its processes by graphically demonstrating the intricacies of just how semiconductor crystals fit upon each other.

Being an executive, Craford takes credit for no individual achievements at Monsanto throughout that time, but said, I was pleased with the truth that, somehow, we were able to be worldwide competitors in every our businesses. However, Monsanto made a decision to sell off its optoelectronics business and offered Craford employment back St. Louis, where he’d have been around in charge of research and development in the companys silicon business.

Craford considered this offer long and hard. He liked Monsanto; he previously a challenging and important job, filled with a large office, oak furniture, an exclusive conference room, and a full-time administrative assistant. But moving back again to St. Louis would end his romance with those tiny semiconductor lights which could create a Dewar glow, so when enough time came, he just couldnt take action.

He did the Silicon Valley walk: next door to the nearest competitor, in cases like this, Hewlett-Packard Co.

Instead, he did the Silicon Valley walk: next door to the nearest competitor, in cases like this, Hewlett-Packard Co. The only real job it might discover that would let him use LEDs was a large step down from technology directora position as R&D section manager, directing less than 20 people. This meant a cut in salary and perks, but Craford took it.

The culture was different, to state the least. Forget about fancy office and private conference room; at HP Craford gets just a cubby, a tin desk, and a tin chair.

And, he told Spectrum, I really like it.

He found the HP culture to be less political than Monsantos, and believes that having less closed offices promotes collaboration. At HP, he interacts more with engineers, and there’s a greater sense that the complete group is pulling together. It really is more open and communicativeit needs to be, with most engineers desks merely 1.5 meters apart. I love the whole design of the area, he declared.

Now he’s got moved up, to R&D manager of HPs optoelectronics division, with a more substantial band of engineers under him. (He still gets the cubby and metal desk, however.)

As a manager, Craford sees his role as building teams, and judging which forms of projects are worth concentrating on. I really do a reasonably good job of staying on the road between being too conservative and too blue sky, he told Spectrum. It will be a negative thing for an R&D manager to state that each project weve done has prevailed, because then youre not taking enough chances; however, we do need to generate enough income for the group on which we sell to remain profitable.

Said Fred Kish, HP R&D project manager under Craford: We’ve embarked upon some new regions of research that, for some people, might have been questionable risks, but George was ready to try.

Craford walks that path between conservatism and risk in his personal life aswell, even though some people may not believe it, given his penchant for adventurous sports: skydiving, whitewater canoeing, marathon running, and climbing. These are calculated risks, in accordance with Craford: The Grand Teton is really a serious mountain, but my son and I took a rock-climbing course, and we went up with a man who is a specialist, so it appeared like a manageable risk.

Holonyak recalls a celebration when a little bit of crystal officially confined to the Monsanto laboratory was handed to him by Craford on the lands an experiment Holonyak was attempting was important. Craford may have gotten fired for that, but he was ready to gamble.

I am hoping to start to see the day when LEDs will illuminate not really a Dewar but an area.

George Craford

Craford can be known as as an irrepressible asker of questions.

His ways of asking questions and considering problems brings people in the group to an increased degree of thinking, reasoning, and problem-solving, Kish said.

Holonyak described Craford because the only man I could tolerate asking me question after question, because he could be really attempting to understand.

Crafords group at HP did work on a number of materials in the last 15years, including gallium aluminum arsenide for high-brightness red LEDs and, recently, aluminum gallium indium phosphide for high-brightness orange and yellow LEDs.

The most recent generation of LEDs, Craford said, could replace incandescent lights in lots of applications. One use is for exterior lighting on automobiles, where in fact the longevity and small size of LEDs permit car designers to mix lower assembly costs with an increase of unusual styling. Traffic signals and large-area display signs are other emerging applications. He could be proud that his groups work has enabled HP to contend with Japanese LED manufacturers and hold its place among the largest sellers of visible-light LEDs on the planet.

Craford have not stopped loving the magic of LEDs. Seeing them out and used is still fun, he told Spectrum. When I visited Japan and saw the LEDs on the Shinkansen [high-speed train), that has been a thrill.

He expects LEDs to be on challenging other styles of lighting and said, I still desire to start to see the day when LEDs will illuminate not really a Dewar but an area.

Editors note: George Craford happens to be a fellow at Philips LumiLEDs. He got his wish and some.

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