During the Paleolithic period, the ancestors began to consciously retain the fire, improve their living environment, not only cooked food, but also the light of the night, the tool to deal with the beast. But until more than a hundred years ago, Edison invented the electric light, and we got the means of light to be transformed. In 2014, the 2014 Nobel Prize in Physics was announced, and three Japanese and American scientists, Isamu Akasaki, Hiroshi Amano, and Shuji Nakamur, were awarded. The reason for the award was "Invented a high-efficiency blue light diode that brings a bright and energy-saving white light source."
Three winners of the 2014 Nobel Prize in Physics
Seeking the light of the night
The unchanging is the natural starlight. But in the past, only the full moon could illuminate the earth. The difference between civilization and civilization is whether we can use our own technology to bring light to the night. In the beginning we could only rely on burning fat. There are many whaling in western countries. Candles are made from whale fish oil. In China, beeswax or animal white wax. Knowing that the oil industry was developed, the cheap saturated long-chain hydrocarbons were used as candles.
Early next year, I hope to see the movie "Current Current", telling Edison's DC VS Tesla's AC.
This way of burning is obviously not safe. So Edison’s story of inventing electric lights is a household name. At the end of this year, Edison will play on the big screen by Bendique Conbabach, and we are expected to see it. Edison's inventions, as well as the improved incandescent lamps, have brought light, but they are characterized by low efficiency.
LED makes today's table lamp design more artistic (Panasonic products)
Today our light source is changing from incandescent and fluorescent to light-emitting diodes (LEDs). But what many people don't know is that in order to find blue LEDs, human scientists have used it for 30 years! It is so difficult to find a blue LED production method with industrial production significance, and finally make up the three primary colors, which can be realized. White light! LED lighting is destined to belong to the century we live now. In this sense, the Nobel Prize is not excessive.
Diodes and light-emitting diodes
Before I talked about Intel history, I said that in the 1950s, when diodes and transistors went out of the laboratory, many companies were doing research in this area, including Texas Instruments, Texas Instruments today. More well-known is the projection technology of DLP.
The earliest LED, but at that time it was infrared light, not visible light.
On June 3, 1957, the third day after James R. Biard graduated from Texas A&M University, he joined Texas Instruments for research and development. He started with the first low drift DC with Walter. Transistor power amplifier circuit. In 1959, Biard worked with Gary Pittman on semiconductor research at Texas Instruments. They first studied the application of gallium arsenide (GaAs) varactors in X-ray band receivers. In September 1961, they jointly discovered the infrared radiation that appeared on the semi-insulating substrate of the forward-biased tunnel diode. So, an infrared conversion microscope purchased from Japan was used to measure the arsenic produced by all Texas Instruments at that time. Gallium varactor diodes and tunnel diodes.
By October 1961, Biard and Pittman demonstrated high efficiency using GaAs pn junction emitter emissions as well as signal coupling and electrically isolated semiconductor photodetectors. On August 8, 1962, Biard and Pittman applied for a zinc-diffused pn junction LED describing a cathod contact with a spacing that effectively emits infrared light under forward bias. The US National Patent Office believes that this patent application and research is earlier than IBM, RCA, MIT Lincoln Laboratory, GE Lab, Bell Labs, and granted US Patent No. 3293513, which is the earliest patent for LED in history.
Is the Nobel Prize fair?
When the Nobel Prize was announced in 2014, many people were very unfair, because the Nobel Prize awarded to LEDs skipped the red and green LEDs that were first discovered, and directly gave blue. The public expression of dissatisfaction included Nick. He Lun Yake, he first invented visible light LEDs.
He Lunak and his red diode
Helenak's laser diodes are the basis of many of today's products.
Nick Helenac holds more than 40 patents, including the patent of the famous semiconductor red laser transmitter, which is the basis of later CD players and cellular phones. Why is He Lunak so cow? We said that Biard was the earliest LED patent, but the infrared rays were produced at that time, and the patent of Helenak’s patent was visible red light! This discovery was published in 1962, when He works in GE (General Electric) research institutes, and the specific principle is more complicated. The name is III-V alloy semiconductor. This red light-emitting semiconductor opens a door to the door of semiconductor lighting.
He Lun Yake, who was in the limelight at the Institute of GE
The commercial red LED, introduced in 1965, costs about $45. But the early LEDs were very inefficient, just illuminating. Not like the incandescent bulbs of the period, the luminescence per watt was only 0.1 lumens, while the level of incandescent lamps was 15 lm per watt.
George Craford invented the yellow LED
In 1972, George Crawford, a student of Helenak, invented the yellow-light LED and improved the luminous efficiency of the diode. In 1976, TPPearsall invented a special light-emitting diode suitable for optical fiber transmission, which has high brightness and high efficiency.
Key blue diode
Red and green diodes are quickly discovered, but to form white light, as a three primary color, the discovery of blue light diodes is difficult. Traditional methods such as phosphorus gallium arsenide cannot be achieved.
Marusaka, 1968
Blue light LED in the earliest laboratory
Early blue LED patent
In 1972, Stanford University's Ph.D. students in materials science and engineering, Herb Maruska and Wally Rhines, used magnesium-doped gallium nitride to make the first blue-violet LED. At the time, Maruska worked with Jacques Pankove on a vacation at RCA Lab. In 1971, one year after Maruska left RCA to Stanford University, his RCA colleagues Pankove and Ed Miller demonstrated the first blue electroluminescent device for zinc-doped GaN, followed by Pankove and Miller. The first actual gallium nitride light emitting diode was fabricated to emit green light. In 1974, the US Patent Office awarded Maruska, Rhines, and Stanford Professor David Stevenson's 1972 patent (US Patent US3819974A). Today, magnesium doping of gallium nitride remains the basis for all commercial blue LEDs and laser diodes. In the early 1970s, these devices were too dark for practical use, and research on GaN devices slowed. In August 1989, Cree introduced the first commercial blue LED based on indirect bandgap semiconductor silicon carbide (SiC). Cree's silicon carbide LEDs have very low efficiency, no more than about 0.03%, but are emitted in the blue portion of the visible spectrum.
Nakamura Hide 2 and Blue LED
The remaining question becomes how to improve the luminous efficiency of the blue diode. In the late 1980s, a key breakthrough in GaN epitaxial growth and p-type doping ushered in the era of GaN-based optoelectronic devices. On this basis, Boston University's Theodore Moustakas obtained a new two-step method for producing high-brightness blue LEDs. Two years later, in 1993, Nikko Nakamura's Nakamura Shuji used GaN growth similar to Moustakas. The process once again proved high brightness blue LEDs. Both Moustakas and Nakamura obtained independent patents, which made the inventor who became a bit messy (partly because Moustakas invented his first, Nakamura first proposed). But in any case, this new development has revolutionized LED lighting, making high-power Blu-ray practical.
The encounter of Nakamura Shuji
Nakamura’s invention can be said to have not been helped by Nichia, because he is not optimistic about the company. He said that he used GaN technology, but the efficiency of this technology is too low. At that time, the general direction in the industry was zinc oxide. And Zinc Selenide, also in this direction, is also studied by Nagasaki University. They experimented almost at the same time and eventually achieved results, and then improved each other's experimental results.
The principle of blue LED
Nakamura that was not valued in Japan at that time.
Nichia also squatted on his patent, only giving the inventor of the blue-light diode 20,000 yen in prize money... The angry Nakamura went to the United States, but he was also asked to sign an agreement by Nichia, and he should not engage in blue-light diode research for three years. . Nichia used the patents sold by Nakamura to sell blue-light diodes. Until 2004, the angry Nakamura sued Nichia for paying the invention compensation and winning the case. The court ruled that Nichia should pay 20 billion yen to Zhongcun compensation. In the end, this amount shrank to 840 million yen. This unprecedented lawsuit has inspired many inventors to seek help in court, many of whom have won litigation or obtained out-of-court settlements. Today, the case of Nakamura v. Nichia has become an indicator case for patent litigation materials.
How can researchers protect their fruits?
Nakamura seems to be more concerned about this judgment of the Tokyo District Court: "The inventor's contribution is not less than 50% even if it is conservatively estimated. The plaintiff has completed the worldwide invention almost by itself."
Two paths from blue to white
After the invention of the blue LED, the RGB three primary colors are combined to emit white light. However, from the invention of red visible light LED to the invention of Nakamura, the human science community has searched for suitable materials and methods suitable for commercial production. It has been used for 30 years, which is why the Nobel Prize was awarded to Nakamura Shuji and Akasaki. Brave masters.
Cheap RGB LEDs have been applied to the keyboard
Approximate white LED obtained by blue light + fluorescence
Another way to obtain approximate white light is to combine the yellow phosphor on the indigo LED, which can also get the approximate white light. It is an economical method. Many flashlights of our flashlights and mobile phones are the products of this technology. .
LED technology is also environmentally friendly and contains no mercury.
There are two outstanding features of LED: high efficiency and long life. The life of LEDs is very long, and basically many factors affecting the service life of LEDs are not due to semiconductors, but to other circuit boards of LED components. The application of LEDs is not much to say. Today, LED bulbs are replacing traditional incandescent lamps, fluorescent lamps, and evolved into different applications in various industries. As far as we can feel, the price of LEDs has dropped a lot in the last decade. .
Intern Editor: Liang Jieying
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