Campus Connection

Nobel Prize Winner in physics to discuss invention that led to LED lamps

A Nobel Prize Winner in Physics who helped revolutionize the way people light their world will give a public lecture at 5 p.m. Thursday, Oct. 13, at UWL. Shuji Nakamura, who was co-winner of the 2014 Nobel Prize in Physics, will speak at 5 p.m. in Skogen Auditorium, 1400 Centennial Hall. He’ll also give a physics seminar at 3:20 p.m. Friday, Oct. 14. His visit is part of a UWL Distinguished Lecture Series in Physics. Nakamura won the prize with two others for the invention of the blue-light emitting diode, which led to the creation of white light used in LED (light emitting diode) lamps. During his public lecture, Nakamura will discuss the history of the invention of blue LED, which proved much more difficult for scientists to create than red and green diodes. He’ll also discuss future uses of LED lighting. “As a non-experimentalist, I'm always fascinated to hear how other scientists get things to work,” says Eric Barnes, chair of UWL’s Physics Department. “At the same time, it sounds like this story is a great example of why society must view science education, as well as research and development, as a long-term investment.” Today LED lighting is considered an energy-efficient and environmentally-friendly alternative to incandescent and florescent light. LED light bulbs have more than 10 times the efficiency of incandescent bulbs, and they last for 50 years. At their current adoption rates, by 2020, LEDs can reduce the world’s need for electricity to the tune of nearly 60 nuclear power plants. Nakamura’s physics seminar will be on the development of indium gallium nitride (InGaN)/gallium nitrate GaN based LEDs and laser diodes for energy efficient lighting and displays. Nakamura will be the 17th Nobel laureate to visit La Crosse as part of a Distinguished Lecture Series in Physics. “The series began in 2000, so we are almost at the point where our first-year students have been alive as long as the DLS has existed,” says Barnes. Barnes adds that students greatly benefit from having personal contact with the laureates during their visit. “They hear that these scientists were not so different from themselves at their age, and they see that their hard work can have significant payoff professionally,” he says. The event is co-sponsored by the UWL Foundation, Department of Physics, College of Science and Health and Wettstein’s. History of the invention Blue, green and red LEDs are needed to create white light. However blue LEDs proved much a more difficult to create than red and green. After about three decades of efforts in the scientific and business community, Nakamura, along with Isamu Akasaki and Hiroshi Amano, of University of Nagoya, used the semiconductor gallium nitride to create efficient blue LEDs, according to the Nobel Prize website. This work during the 1980s and 1990s revolutionized lighting with creation of LED lamps. Biography Shuji Nakamura joined Nichia Chemical Industries Ltd in 1979. In 1993 and 1995, he developed the first group-III nitride-based high-brightness blue and green LEDs. He also developed the first group-III nitride-based violet laser diodes (LDs) in 1995. Since 2000, he has been a professor of Materials and Electrical & Computer Engineering at the University of California, Santa Barbara. Physics seminar abstract LEDs fabricated from indium gallium nitride (InGaN) have led to the realization of high-efficiency white solid-state lighting. Currently, InGaN white LEDs exhibit luminous efficacy greater than 150 lm/W, and wall-plug efficiencies higher than 60 percent. This has enabled LEDs to compete with traditional lighting technologies such as incandescent and compact fluorescent lighting. Further improvements in materials quality and cost reduction are necessary for widespread adoption of LEDs for lighting. Tunnel junction (TJ) was used to improve the light extraction efficiency and the p-type contact in order to reduce the operating voltage of the LEDs. Peak wall-plug efficiency as high as 70 percent have been achieved. A review of the unique polarization anisotropy in GaN is included for the different crystal orientations. Emphasis on semipolar LEDs will highlight high-power violet and blue emitters and considers the effects of indium incorporation and polarization. Semipolar GaN materials have enabled the development of high-power blue lasers. Laser light sources show great promise for directional white illumination with efficiency as high as 87lm/W.