 Winter 2005 |
| Faculty Profile | |
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Let There Be Light-Emitting Diodes (LEDs) Professor Russ Dupuis talks about the development and Interviewed by Jane M. Sanders |
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RUSSELL D. DUPUIS is a professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology.
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Dupuis and two colleagues were awarded the 2002 National Medal of Technology as inventors and innovators in the light-emitting diode (LED) technology field for a combined 40 years of contributions. Today, LEDs are used in digital displays, consumer electronics, automotive lighting, traffic signals and general illumination.
A: It is clear that LED use is growing and will become ubiquitous. LEDs have already replaced incandescent lighting in many lobbies, museums and even the Jefferson Memorial in Washington, D.C. It is now lit with white LEDs, which make Jefferson’s writings engraved in granite there easier for visitors to read from the ground level. So it’s not just a trick. There is some value to it, not to mention the energy savings.
What we can say about solid state LEDs is, “You ain’t seen nothing yet.” Right now, people see LEDs as having specialized applications, such as in the side and tail lights of 18-wheeler trucks and buses and as tail lights in high-end cars, such as Cadillacs, Mercedes, Audis and BMWs. LEDs are so reliable. They don’t have to be replaced often, if ever. LEDs will be used in the headlights of the Audi A8 in 2006, and other car manufacturers will follow.
In regular offices, LEDs will eventually replace incandescent lights because the old technology is so inefficient. So much energy is wasted because incandescent lights put out heat. The calculations show we could cut the need for 33 nuclear power plants if LEDs replaced traditional lighting. Edison’s bulb is a wonderful thing, but it’s very wasteful. With all due respect to Mr. Edison, we’re encroaching on his space. At some point, all incandescent bulbs will be in museums. People will say, “You mean they just ran current through it and heated it up? What kind of wasteful insanity is that?”
There are good physical reasons that LEDs are the ultimate way to create light from electricity. In principle, they are 100 percent efficient internally. You have to argue with Mother Nature about how to get the light out of the crystal and into free space, so you never really get 100 percent out. But there’s no other thing produced with an internal efficiency of 100 percent that can be used so effectively in compact form. There are competing technologies – primarily diodes made from organic polymers. But they have their own value and problems. For now, the multi-billion dollar LED industry will be the primary source of solid state light for a long time.
LEDs will become the dominant form of lighting in high-end buildings within the next 10 years because designers see energy use as part of the total picture. In commercial space, it’s important not to have lights burnt out. People might say, “This is some kind of cheap scam place, and I’m not going to shop here.” So, often businesses replace incandescent lights before they burn out. What if you had to do this only once every 10 years or even never? You could save the energy, the hassle, the interruption, the environment. It’s the same thing in cars. You increase the reliability, save a little weight and space and improve your mileage.
LEDs will eventually be used in all offices and then in homes. Incandescent and fluorescent lamps are a form factor for these products. LEDs have a different form factor. But for a while, we’re stuck with these bulb-like things. People are not familiar with LED-designed things that function the same but are different devices to light the room. They need this Edisonian screw-in device that is not very practical for LEDs.
QUESTIONS:
1. How might the use of LEDs be expanded in coming years?
2. If Thomas Edison was alive today, what do you believe he would think about the advances you and your colleagues have made in LED technology?
3. What were the major technological challenges in the development of LEDs that you and your colleagues conquered during the past 40 years?
4. How did you perfect the process of metal-organic chemical vapor deposition (MOCVD) to grow high-quality semiconductor thin films and devices? And how did it improve LED technology?
5. Why did you decide to pursue development of MOCVD technology after many in your field disregarded it? And how did your colleagues respond to your work initially and then later after your published your results?
6. What do you view as your contribution to making LEDs replace the light bulb?
7. Since joining the faculty of Georgia Tech in August 2003, you have begun exploration of nanoscale “self-assembly.” What is that and how will your research with LEDs affect this nanotechnology work?
8. Why did you choose a career in electrical engineering?
9. How did your childhood and teen-age experiences affect your interest in science and technology?
10. How did the influence of your personal and/or professional mentors affect your work ethic and ultimate achievement?
11. What do you enjoy doing when you’re not working?
1. How might the use of LEDs be expanded in coming years?
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Professor Holonyak’s interest was in visible light emitters because visibility is important to humans for information displays and other devices. Since he created the first visible LEDs, the term has come to refer to visible light-emitting devices of gallium, arsenic and phosphorus origin. Developing visible LEDs was not just a simple extension of LED technology. It required a lot of perseverance and skill. In the 1960s, materials like alloys – three-element compounds – were thought to likely be unusable because they are crystalographically and chemically random. They are not ordered materials like silicon or diamond or gallium arsenide. But Holonyak pushed the edge into unknown territory and added his own special wrinkles to the process of creating LEDs.
These first visible LEDs were commercialized by Monsanto, which was once the largest supplier of semiconductors…. This technology came directly out of Holonyak’s lab, and he is proud of it. The technology was very applicable to real human needs, and he has always wanted technology to lead to products that better the human condition.
Holonyak’s creation of visible LEDs is now called the “Alloy Road” in semiconductor technology. It formed the underpinnings of virtually everything we know today that is not silicon itself. Today, billions of LEDs are made each month around the world, and those are all made from alloys – four-element alloys for yellow and red LEDs and three-element alloys for the newer blue and green LEDs and their cousins the white LEDs. The alloys today are more sophisticated than the original ones. They’re grown with a different, more complicated process – called metal-organic chemical vapor deposition or MOCVD – that I developed and improved in 1977 while at Rockwell International. Now, MOCVD is the only technology used for the commercial manufacture of all colors of high-brightness LEDs
The third part of this trio who won the award is George Craford, who was also one of Holonyak’s students. He led the LED development effort at Monsanto and developed the first practical yellow, or amber, LEDs. Craford is now at LumiLeds, (previously the Hewlett Packard Optoelectronics Group), the world’s leader in this technology for high-brightness devices.
Over the past 40 years, this technology has gone from low-performance red LEDs to very high-performance, full-color displays like the one at Times Square in New York City. It is essentially 16 million LEDs in one display, and a larger one is under construction there. This same technology comes to individuals in the form of cell phone and laptop backlighting, green traffic lights, high-intensity flashlights and specialized architectural lighting in museums. For example, the Beatles’ “Sgt. Pepper’s Lonely Hearts Club Band” costumes on display in the Metropolitan Museum of Art are lighted with high-brightness LEDs so the colors will be truer and the lights won’t degrade the material like light bulbs would.
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That’s important because aluminum is in virtually all high-brightness LEDs. You don’t get too far on the Alloy Road without it. Aluminum gives you the freedom in semiconductor land to wander about and add colors to the palette that you couldn’t reach without it. So LEDs are critically dependent upon aluminum.
In the mid-1970s era, it was clear that anything with aluminum compatibility was valuable, and the fact that is was compatible in the vapor phase made it even more valuable for production of large quantities of devices.
When I started working on this process, MOCVD was routinely dissed for creating materials that were full of impurities. It was an inherently dirty process from the semiconductor point of view. Two principal impurities were carbon and oxygen, which are common in the world, but contaminate semiconductors in most cases. A lot of people thought these impurities couldn’t be removed from MOCVD. They thought this was wacky.
But if you’re careful about when you use these chemicals at the beginning, middle and end of the process, then you can make some nice materials. So my first attraction to MOCVD was its aluminum compatibility. Then that drove me to fix the other problems using the technology available at the time. We’re still improving on the purity of these materials. Impurities are the enemy.
After I published my work with MOCVD, within 10 years the technology was widely accepted. Technology can move very quickly in some cases, and in other cases, there is so much underpinning needed to make it practical. Then you need market drivers, too.
We’re still waiting for someone to replace the 75-cent light bulb. Someday we’ll have sunlight LEDs, but it will take a long time to get there. One day children will see incandescent bulbs in a museum and wonder why people used those yellow-looking things.
6. What do you view as your contribution to making LEDs replace the light bulb?
A: If you took away MOCVD, the LED world would collapse completely up to this point. There’s no other technology in use right now for creating high-brightness LEDs. It would take a huge research investment to bring a competing technology up to the performance level and efficient manufacturing cost that MOCVD provides. MOCVD is the winner for the foreseeable future, and I’m pretty happy about that because I did part of it. Of course, I wasn’t the only person working on MOCVD then, but my work prompted others on the Alloy Road to use the technology. People didn’t believe it could be done at first, but I had the data, and eventually – two years later – others made the same devices using MOCVD. But we were in the lead by then.
When Holonyak left GE to go to the University of Illinois, Bill Packard wanted him to set up their LED research group at Hewlett Packard. If he had done that in 1963, he’d have been a multi-millionaire a long time ago. He chose to be a professor, and he says he’d still choose this route again because he’s had so much fun doing research and being at the front edge of a lot of things…. I came back to academia after working in industry for 15 years because of what I saw Nick Holonyak doing in his career. We like seeing the benefit from our work going into industry. There’s a joy from seeing it go into products.
7. Since joining the faculty of Georgia Tech in August 2003, you have begun exploration of nanoscale “self-assembly.” What is that and how will your research with LEDs affect this nanotechnology work?
A: To date, we’ve been making semiconductors like we did in the 1960s. Now we’re exploring the possibilities of nanoscale self-assembly to manipulate materials at a fundamental level. Today, we make LED materials on the microscale level. Next, we want to take semiconductor element atoms and assemble them in a different way using different rules that we’re still discovering.
It’s an interesting exercise. We’re forming assemblies of atoms in sets of tens or twenties, not 10 or 20 millions like LEDs are made today. LEDs take a large chunk of real estate today. We work on planar geometric layers – x, y and z. Nanostructures destroy 3-D symmetry. We’re building one-dimensional elements with different electrical structures because they are so small….
For now, we’re approaching this process from a slab, not a single atom, point of view. But we’re attempting to build materials on the order of thousands or hundreds of atoms instead of millions or tens of millions. To do that, you can’t use crude tools or chemicals. You must use self-assembly, or Mother Nature’s rules such as those for stress, strain and localized physical features. We need to know how to get her to do this for us….
The goals are faster speed, increased efficiency and better ways for processing and storing information. It could result in faster computers and better LEDs. Holonyak and I still work together, and we were the first to show visible LEDs using nanostructures in the active region. At Georgia Tech, we’re growing diamond lattices that are bumpy, not smooth and planar like a piece of glass. They look like golf balls, but they’re 10 nanometers on a side. The performance of LEDs will depend on nanoscale properties such as these.
8. Why did you choose a career in electrical engineering?
A: I’m a farm boy, but I didn’t like the farm because I have hay fever. I always liked science and math. I tinkered with things more. I liked taking things apart, like my bike.
In high school, my cousin had a boyfriend who was studying electrical engineering at the University of Illinois. So I asked him, “What do you do?” It seemed more interesting than other types of engineering because there is more physics involved. I ended up earning all of my degrees at the University of Illinois. I never looked back. My fraternal twin brother went into veterinary medicine, and practices near Naperville, Ill.
9. How did your childhood and teen-age experiences affect your interest in science and technology?
A: My mother was a teacher. She started her career when she was 18 and taught in a one-room schoolhouse. My dad was a farmer and liked to fix things, and I would help.
There were 130 students in my high school and 36 in my graduating class. My kindergarten through 12th grade academic training was not that good. But my brother and I did fine in college at the University of Illinois in Urbana. He went to the U of I veterinary medical school and got his DVM degree. I completed my Ph.D. in electrical engineering, and we both graduated as undergraduates with “Highest Honors.”
10. How did the influence of your personal and/or professional mentors affect your work ethic and ultimate achievement?
A: Ben Franklin said, “Plow deep while sluggards sleep.” I like that farm motif. While others are goofing off, you work. My parents were not poor, but they always worked hard for what they had. My dad was a farmer during the Depression. He had an eighth grade education because he had to work on his father’s farm instead of going to high school. He was the oldest son of an Illinois farmer – with his origins in a French-Canadian farming family that had moved from Quebec and settled in Illinois in 1853. He had to borrow 50 cents from his father to take my mother to a dance when they were dating. He had to work until he was 37 years old before he could afford to be married.
When my mother was 39, she had her first child, my older brother. Back then, teachers had to quit when they got pregnant. So in 1939 or ‘40, when my parents were offered a farm to rent through relatives, they did it. The house had no electricity or running water. My mother was used to electricity because her family’s farm had a diesel generator. So she got married and then had to go back to using kerosene lamps and wood and coal cooking stoves.
At first, my dad farmed with horses. It was not easy. Eventually, he bought gasoline-powered tractors to replace the horses and he bought his own farm when I started high school.
11. What do you enjoy doing when you’re not working?
A: I have one hobby that I occasionally indulge in. It’s genealogy. Oh, and I’ve always liked to build model airplanes, even as an adult. But in researching my family, I found that my 11th-great grandfather, Louis Dupuis, was from Paris, and he came to Quebec City as a soldier in the French Army in the 1680s. His father was a lawyer in Paris – a “Collector of Fines for the Abbey of St-Germain-des-Prés” (the oldest church in Paris). Louis left the French army in 1688 and became associated with the Quebec fur trade and was very active in many canoe trips to trade with the Native Americans in what is now Upper Michigan. Eventually, he settled in Montreal. He was kind of a wild guy, which was interesting to find out.
Then my great-grandfather was a young boy when he left Quebec (in 1853), and he joined the Union Army as a 16-year-old recruit in 1861 or so. He was not a fighter, but he was in the quartermaster corps. He drove teams of oxen pulling wagons loaded with supplies. During the Civil War, my great-great grandfather supplied horses to the Union Army. He made a lot of money during the war helping the Union Army find good horses.
For more information, contact Russ Dupuis at 404-385-6094 or
russell.dupuis@ece.gatech.edu.
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Last updated: April 3, 2005