Abstract: For young people at Tsinghua University, it is worth explaining how GaN and related materials have affected our lives. The most important application of GaN and related nitride materials has been the development of blue LEDs. Portable game machines, cellular phones and smart phones are very common items, especially among young people. The world’s first portable game machine was released in 1979 and cellular phones first became commercially available in 1984. However, until the end of the 1990s, all the displays of portable game machines and cellular phones were monochrome. Thus, it should be emphasized that the younger generation can now enjoy full-color portable games and cellular/smart phones because of the development of blue LEDs. Today, the applications of blue LEDs are not limited to displays. In combination with yellow phosphors, blue LEDs can act as a white light source and are used in general lighting. By 2020, about three-quarters of the incandescent and fluorescent lamps in Japan will have been replaced with LED lighting systems, resulting in a reduction of electricity consumption by 7% in principle. Therefore, I would like to recommend that people in China to use LED lighting systems to reduce CO2 emissions. Today, more than 1.3 billion people live in China and the consumption of coal

in China exceeds half of the total world consumption. By using LED lighting systems, you can reduce the consumption of coal and CO2 emissions.

The applications of GaN and related materials are not limited to blue LEDs. They can be used for deep-UV (DUV) LEDs by utilizing Al-containing AlGaN. According to a UNICEF report, 663 million people still cannot drink safe water, and 2.4 billion people do not use safe sanitation facilities. In addition, global warming is causing an increase in the number of bacteria in drinking water even in developed countries. AlGaN-based DUV LEDs are effective for the low-cost and simple sterilization of water. Recently, DUV LEDs with an output power of over 50 mW/chip have been realized, and can now be installed in compact water purification systems.

Another application of these materials is laser diodes (LDs). Nitride-based violet LDs are the light source of the large-capacity optical storage systems called Blu-ray discs. Today, nitride-based LDs combined with phosphors can be used for the long-distance beam headlamps of vehicles. This material system is also useful for electron devices. In mobile or smart phone base stations, high-frequency RF amplifiers employing GaAs-based heterojunction field-effect transistors (HFETs) are being replaced with those employing GaN-based HFETs

because of their capability of higher-power operation. By replacing Si-based insulated gate bipolar transistors and super-junction MOSFET power devices with GaN-based power devices in inverter and converter circuits, we can expect a 9.8% reduction in electricity consumption in Japan.

In this presentation, I would like to explain the future prospects for new applications of group III nitride semiconductors and their contribution to establishing a sustainable society.

All are welcome.