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A Light Bulb Goes Off: A Conversation with Hiroshi Amano

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From the Summer 2015 Issue "Climate's Cliff"

A Conversation with Hiroshi Amano

In 1879, Thomas Edison invented the light bulb. For nearly a hundred years, the incandescent bulb—which worked mainly by electricity passing through a filament and heating it to incandescent temperatures in a glass globe—lit up the world. It was effective in terms of turning night into daylight, but most inefficient in virtually every other way. It used, indeed wasted, a lot of electricity, generated heat, and had to be thrown away once it burned out in a relatively short time. Along came the next phase—fluorescent lights, with their own set of problems. But scientists continued working and eventually came up with the process of electroluminescence, and in turn light-emitting diodes or LEDs. For nearly three decades, though, there were only two types of LEDs—red and green. The third vital color, if they were to be combined into a bulb that emitted white light, was blue. And for nearly four decades, this eluded scientists. Until one day, following years of effort, three extraordinary Japanese scientists stumbled on the way to make blue. For their efforts, last year, all three were awarded the Nobel Prize for Physics. One of them was Hiroshi Amano, a professor at Nagoya University located on Japan’s Pacific Coast. World Policy Journal editor and publisher David A. Andelman spoke to him for a Conversation on his epic breakthrough and his astonishing work that comes next—and could lead to another Nobel Prize. 

WORLD POLICY JOURNAL: I’d like to talk to you a bit about how you and your colleagues effectively enabled the creation of the light-emitting diode (LED), which is  really the greatest single advance, in many ways, of energy conservation. To start, can you share how the LED differs from traditional light bulbs, and how you came to make this discovery?

HIROSHI AMANO: The LED is a fourth generation artificial lighting system. The first one was the wire or frame based on conduction. The second one was incandescent. The third is the fluorescent lamp. But the problem is that the florescent lamp needs a vacuum and also has a glass tube, which is very fragile. So the LED is the fourth generation, which is based on the solid state and the quantum mechanics based lighting system. It is very tough and very efficient—indeed the most efficient lighting system.

WPJ: And what I especially found interesting is that basically you need three colors to arrive at the LED light. You need red, green, and then blue. It was very easy to get the red and the green, but it was the blue that you discovered—that took 30 or 40 years to do— that really enabled this?

AMANO: You are right. For red and green it is not so difficult because the crystals that emit red light and green light are relatively easy to grow, but the crystals that can emit blue light are quite different and very difficult to grow. That is why it took a long, long time to realize the blue-light emitting diode.

WPJ: So how were you able to arrive at that?

AMANO: Semi-conductor physicists already knew which crystals could emit blue light, but the problem was that growing single crystals is very difficult.

WPJ: How did you do that?

AMANO: Today’s blue emitting diode is based on gallium nitride. To grow the gallium nitride by direct reaction of gallium and nitride, we need very high pressure—over 45,000 atmospheres—and very high temperatures. Then we need to use the chemical reaction to reduce the pressure and the temperature. We have to use the different crystals as the substratum wafer to grow the LED structure. So the sapphire is one of the best candidates for the substrata, but the problem is that the periodicity between the atom arrangement of the sapphire and the gallium nitride is quite different—16 percent different.  So many people tried to grow single crystals but failed, and for a long, long time. In general, the semi-conductor physicists tried to grow crystals at high temperatures, but in our case we did it at low temperatures. That’s why we succeeded.

WPJ: I understand in a lab you have controlled conditions or you can replicate all sorts of interesting conditions that are very difficult on an assembly line. How did it get from that point to the point where we can have a very simple LED light? How did you get from that to an ability to manufacture that on a mass scale worldwide?

AMANO: We succeeded in mass production because we realized the low temperature phosphor technique to grow high quality crystals, and also we succeeded in realizing the p-type gallium nitride. Before us, many people tried to replicate LEDs based on gallium nitride, but no one succeeded in the p-type nitride. We, however, succeeded in the p-type gallium nitride.

WPJ: We now have in the United States virtually universal adoption of the LED, and many other areas of the world as well.  One member of the Nobel Prize committee pointed out that a quarter of all electricity produced in the world is devoted to illumination. So could you venture a guess as to how much energy your discovery is saving the planet?

AMANO: Take Japan’s case. Maybe by 2020 about 70 percent of the general lighting can be replaced by the LED lighting system by which we can save about 7 percent of the total electricity in Japan. Maybe in the world the trend is a bit slower. In the case of the United States, by year 2030, about 70 percent of the general lighting can be replaced by LED lighting and about 7 percent of electricity saved by LED lighting systems.

WPJ: Japan is trying to move away from nuclear energy and toward conventional or new types of energy. Might this help in this process because less electricity will be necessary for lighting?

AMANO: In Japan, before 2011, about 30 percent of the electricity was generated by nuclear power plants, but today all of the nuclear plant production has stopped. So we have to find the way to obtain the 30 percent. About 7 percent can be saved by LED lighting, so we have to search for another 23 percent in savings.

WPJ: The other issue that’s interesting about LED use is that they are so much cooler than incandescent lighting. And for those concerned about our warming planet, might replacing incandescent light bulbs all over the world with LEDs effectively contribute to lowering, or at least slowing, some of the heating at the surface of our planet?

AMANO: You are right that the incandescent lamp emits infrared radiation, but I’m not sure how much it affects global warming systems. In Japan, there is another opinion. For example, in the Hokkaido area it’s very cold, and it snows. In the traffic systems, if the traffic signals are covered with snow, in the case of LED light signal systems, there is no heating, or the heating is very small, so they cannot melt the snow. So we have to find another route.

WPJ: Now it also seems that because less electricity is required to power an LED than an incandescent light, there are so many parts of the planet, especially the more remote regions of the world, where the need to generate the larger quantitates of electricity to power a village lit with incandescent lights is being replaced by a far smaller energy generating need. So might we then be able to light up hitherto darkened regions of our planet where this might not have been possible before? 

AMANO: Yes. That’s a very important point. In the case of LEDs, by combination of solar cells and batteries, we can provide very simple lighting without electrical generation. For example, I met with the Minister of Education of Mongolia, where they still live without houses—they are nomads. Now they can provide very simple lighting tools by combining solar cells, batteries, and the LED lighting systems, which provide the students, or children, with a lighting system. So the children can read a book, or study, even at night. 

WPJ: What motivated you to develop this whole system? Was it purely scientific curiosity? Or was it a sense of the needs of our planet? How did his happen?

AMANO: When I was young, my interests were purely scientific. However, now my interests, or my motivation, are how I can contribute to the planet, or to the people living on the planet.

WPJ: So you think that the scientific community in general has a responsibility to commit to work on addressing these threats to our planet, or the prospects of improving it. What role do you think science should play in making mankind better?

AMANO: In my case, I can contribute to the energy saving, or energy efficiency, issues. Maybe I can also contribute not only LEDs but also the other devices such as power devices or solar cells, and I do believe I can provide much more efficient devices or solar cells in the future.

WPJ: So your next work is in the solar cell area. The research you’re beginning now is the backside of the LED—how to generate the electricity needed to power the LED.

AMANO: My interests now are not only LEDs, but also the solar cells and also the power device, for example the inverter or converter. The solar cells generate Direct Current (DC); we use Alternate Current (AC) in homes. We have to change the electricity from DC to AC. So we use an inverter circuit system and also a converter circuit system—effectively a switching transistor. If you considered an electric vehicle, the batteries are DC, but the motor is AC because of the high efficiency generated compared to the DC motors. We have to change the electricity from DC to AC, so we need an inverter system. And we use the power transistor. Efficiency is still high—95 percent—but 5 percent is lost.

WPJ: Do you think you can get to that last 5 percent? 

AMANO: Yes, the last 5 percent we can reduce to 0.5 percent by using the new materials system.

WPJ: What kind of materials?

AMANO: That’s the gallium nitride and the silicone carbide.

WPJ: Oh so very similar to the materials that go into your LEDs then?

AMANO: Right. We are also now concentrating on fabricating new power transistors based on gallium nitride and silicone carbide.

WPJ: That’s what your research deals with now. And that will be your next advance. Now let’s go back to the LEDs. You said last year that about half of the blue LEDs in the world are manufactured in China and that energy conservation efforts can be enhanced by cooperation between the research of Japanese universities and China’s production capability. So how do you see these global efforts going forward and developing? Should Japan and China lead the way in all of this?   

AMANO: In China, the factory size is much, much bigger than in Japan. I think that the collaboration with Japan’s ideas, or the universities, and China’s manufacturing capabilities will help LEDs penetrate the global marketplace much faster.

WPJ: So basically Japan has some extraordinary people like you who are great scientists and inventors, developers of new and great techniques, and China can take those and develop them for the world more effectively on a massive scale. Are you happy that Japan is taking this kind of leadership in the scientific area?

AMANO:  We are very proud of providing the ideas or technology to people who are trying to fabricate these devices or who try to realize our ideas.

WPJ: How long do you think before your new devices will be ready to take their place beside the LED to make important changes in society? What is a realistic timeframe to expect in the future going forward for this type of transformation?

AMANO: In the case of our blue LEDs it took about 30 years from the start of our studies to then contribute to the energy savings. A long time is necessary to realize the idea.

WPJ: So is three decades a reasonable period? Is this what we can expect as the norm from, say, the scientific laboratory to the factory to the consumer in this day and age? Or do you think such a process can, and should, be accelerated given all of the needs of the world in terms of conservation and our energy needs?

AMANO: In the case of blue LEDs, there were many candidates. But a long time was necessary to understand which was the best candidate. There were many competitions until we finally found the best solution. 

WPJ: I would like to conclude by asking you about what aspect of your work holds for you the greatest hope for the future of people on our planet?

AMANO: The health of the people, because we are now trying to fabricate LEDs by which we can clean up the water or clean up the air. More so, other people are trying to use LEDs for purifying for food.

WPJ: So these are new applications for the LED other than lighting a room. Indeed, the LED has already changed so much in the world. By replacing sodium lights with LEDs, the whole tone of major cities is being changed—the lighting so much more sharp, bright, and realistic than under the sodium lights. In short, it has changed the lives of so many people. Are you moved by that? Are you pleased you’ve affected so many lives so positively?

AMANO: I am very proud, but I’m not the only person to contribute to this. Many people have contributed to realizing the LED’s applications, so I owe much to the people who are trying to develop LED’s technology.

WPJ: Well that’s very modest of you, Professor Amano, but without you, they would have nothing to work with. I congratulate you and celebrate you, as do we all here.

AMANO: Thank you so much



[Cartoon courtesy of Jeff Danziger]



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