The hardships behind the Nobel prize: blue LED

Mobile phone screen, outdoor large screen...... Nowadays, LED (light emitting diode) is more and more widely used in display and lighting because of its energy saving and high efficiency.

The most important cornerstone for the massive use of LED is the foundation of the Japanese scientists, Amano Hiroshi, and Nakamura Shuji. In 2014, they won the Nobel prize for physics for the invention of blue light-emitting diodes (ie, blue LED).

Left: Akasaki Yong, Amano Hiroshi, and Nakamura Shuji

On the afternoon of March 11th, Amano Hiroshi, a professor at Nagoya University, gave a speech at the Shanghai science hall, sharing his experience with the discovery of blue LED and the application of LED. The speech obtained by the Shanghai Municipal People's Association for friendship with foreign countries, Shanghai, Japan Association of Magnolia award.

Amano Hiroshi and his mentor, Akasaki Yong, chose a less promising compound as a research direction compared with other scientists who were working on the discovery of blue LED. He said this may be a lucky, let him win in not much competition on the road, but in the process of hard as can be imagined.

"At that time, I was not particularly aware of the difficulty of this study, the beginning of the study to look at the LED display, is to facilitate the world, based on this idea to stick down. "

There are many from Fudan University, Tongji University, physics majors lecture, Amano Hiroshi finally told "if you have sincere words and earnest wishes, hesitate in the course of the study, I hope you can return to the starting point of your dreams, think about why to do this study. "

Tianyehao

At first, the research direction is not optimistic

In twentieth Century, the use of incandescent lighting is the main. In the late nineteenth Century, Edison invented the lighting tool, the principle is to heat the filament to incandescent state, the use of thermal radiation emitted visible light source. One can imagine that in the process of incandescent light, a large part of the energy has been distributed to heat out, the loss is very serious.

1960s American scientists invented the red LED. Compared with incandescent lamps, LED lighting needs low voltage, low current, high luminous efficiency, and become a new research focus of the lighting source.

The primary colors of light are red, green and blue. In other words, these three colors of light mixed, to produce white light. After the invention of the red LED, in order to make LED commercially available, the invention of green and blue LED has become the focus of scientific research.

In 1974, green LED was developed. After that, scientists have focused on the blue LED on silicon carbide (SiC) and zinc selenide (ZnSe) and gallium nitride (GaN).

At that time, many people have tried on GaN failed, looking to look more promising on the other two materials.

But there is no loss of confidence, that is, Professor Amano Hiroshi's teacher, Professor Akasaki Yong. Akasaki Yong was doing research in the enterprise, GaN has not been the focus of the study of blue LED, many people advised him not to do this research, Akasaki Yong put the research to the Nagoya University. In 1982, after graduating from the University of Amano Hiroshi into the studio, began to contact the blue LED R & D work.

In a popular material input, there is no funding is not optimistic, the road of the study at the beginning of the beginning of the rugged, but Tian Hao but do not care, but a headlong into the hard research.

Sometimes I think this is a kind of luck, in the direction of the last few people compete with you, can concentrate on research. "

After the invention of the blue LED, LED lighting has become possible

Amano Hiroshi recalls, when R & D blue LED has three major difficulties: one is unable to form a high quality gallium nitride crystal, second P type Gan can not make a knot, third is not high illuminance indium gallium nitride crystal.

"At that time I thought that if the blue LED can be successful, you can create a new monitor, which is a major event that can change the world. "Tian Hao Hao said that he started this research, initially with the idea of benefiting the world.

After entering the studio Akasaki Yong, Tian Hao Hao and other students along with Akasaki Yong into Gan research.

At that time, the research funding is very difficult, they need the price of the experimental device is about one hundred million yen, but the studio funds only -310 million yen. In order to carry out the research, the students have to discuss their own experimental device, using a variety of "soil" to overcome difficulties.

Amano Hiroshi shows a photo of their own experimental device, "there's a beer bottle in the picture. The coil is used in the experiment, and the size of the coil is exactly equal to the diameter of the beer bottle. "

Amano Hiroshi undergraduate 3 years, master's degree in the study of gallium nitride has been invested for 2 years, but did not see the synthetic hope. At that time the family does not support he Sike this study has stopped his tuition, but luckily he won a scholarship, it may continue to PhD courses.

In the last year of the master, Amano Hiroshi was inspired by a teacher in a discussion, the idea of making a low temperature buffer layer on a sapphire substrate, and then the method of making gallium nitride single crystal. The experiments show that this method can be used as a gallium nitride crystal with a high degree of crystallization, which is regarded as one of the breakthrough technologies of blue LED.