The blue LED.
You may consider it a pretty mundane aspectof modern life, largely relegated to simple tasks such as indicating power and illuminatingholiday lights.
Ubiquitous as they are now though, they’rea relatively recent invention, and until 1993 there was no such thing as a commerciallyviable blue LED.
Yet without them so much of our modern techwould not be possible, from cell phone displays, to energy-efficient light bulbs, to that blue-lit button on the front of your toaster.
Blue LEDs were such an important advancement that inventors behind it were awarded the Nobel Prize in 2014.
What happened? This is LGR Tech Tales, where we take a lookat noteworthy stories of technological inspiration, failure, and everything in-between.
This episode tells the tale of the decades-longstruggle to create the blue LED.
Our story begins in 1907 with the emergenceof the light-emitting diode.
Henry Joseph Round discovered that if youtouch two metal needles to a crystal of silicon carbide and apply electricity, you’d sometimessee a very dim light glowing color.
Silicon carbide, while often used in thingslike sandpaper, is actually a semiconducting material, and the electrified needles createda diode, hence: light-emitting diode, or LED is what it was called.
But while this was experimented with for years, including notable examples by Oleg Losev in Russia in the 1920s, it took decades fora practical LED to be produced.
An important step in this direction came from Dr.
Rubin Braunsteinat RCA in 1955 that showed an infrared emission from semiconductor alloys like gallium arsenide.
This was followed up in 1961 at Texas Instrumentsby James Biard and Gary Pittman, who discovered a 900nm near-infrared light emission on agallium substrate.
The same method would also be used at General Electric to create a more visible LEDthrough the work of Nick Holonyak Jr.
His diode showed a defined, yet faint, red light visible to the naked eye.
Over the next decade, various chemical compositionswere used to produce yellow and green LEDs as well, which in turn helped inform the future improvement of the others.
These red-orange LEDs proved to be some ofthe brightest and most cost-effective to manufacture, initially sold to the military and companieslike Hewlett Packard, before appearing in consumer products like the pocket calculatorsof the early 1970s.
Soon, LEDs were popping up in electronicsall over the place, finding uses in everything from computer displays, to telephone keypad lighting.
However, there was still a primary color thatremained elusive.
The idea of a blue LED was highly desirablesince blue light is a crucial part of producing a full spectrum of color.
The three additive primary colors of red, green, and blue can be mixed to create other colors between them, and then combine completelyto create white.
And the reason LEDs were stuck with varioushues of red, yellow, and green, but not blue, is down to the physics in how light is producedon a diode to begin with.
To put it very simply, an LED is made up of multiplelayers of positive and negative semiconductor materials, and when electricity passes through them, they emitlight at the frequency the materials allow.
In order to achieve a specific color and brightness, each LED needs precisely the right configuration of materials on the semiconductor die.
And since the frequency interval of blue lightis much higher than red, yellow, and even green, it required far more exotic materials andproduction processes to reproduce.
Some of the early blue LEDs were developedat RCA in 1972, while attempting to come up with a television that used LEDs instead ofphosphors in cathode ray tubes.
That breakthrough was achieved at RCA that yearby Herbert Maruska, accomplished by first figuring out how to grow crystals of galliumnitride, and then “doping” them with magnesium.
But unfortunatelythe resulting light was too dim to be practical, and seeing as RCA was in financial troublegoing into the mid-70s, further development was halted.
So, gallium nitride and magnesium.
The groundwork was there, but there were hugeobstacles to overcome to make this light bright enough to be useful and cheap enough to bepractical.
Companies like Bell Labs and Matsushita continuedworking with these materials for years, before coming to the conclusion that gallium nitridewas unlikely to result in viable blue LEDs since it was so tough to work with.
Growing the crystals in high enough qualityand quantity was stupidly challenging, and reliably producing the exact types of positiveand negative layers required was even harder.
It was not until the 1980s that these obstacleswould be overcome, and it was largely thanks to a string of breakthroughs by threemen in Japan.
The first is Isamu Akasaki, who was a physicistat Nagoya University leading a group in coming up with a better method of growing galliumnitride.
Next is Hiroshi Amano, an undergraduate researchingthe growth of nitride semiconductors, who joined Akasaki’s group in 1982.
And finally we have Shuji Nakamura, an electronicengineer specializing in semiconductor tech at the Nichia Corporation in Tokushima.
It was in 1985 that Amano first had promisingresults in making high quality gallium nitride by using what the team called ‘low-temperaturebuffer layer technology.
’ This was an important step to growing highquality crystals, but it didn’t solve the problem of producing an efficient positiveand negative junction.
That didn’t happen until 1989, when Akasaki’sgroup finally succeeded in fabricating the correct layers by irradiating the crystalswith a high-powered electron beam.
The results still were too complicated andcostly to be used commercially, but the results and the research were made available for peopleto read.
People like Shuji Nakamura, who was workingon creating new products for the Nichia Corporation.
At the time, Nichia was known for producingphosphors used in fluorescent lights and color cathode ray tubes, but were looking for afresh new product with fewer competitors.
Nakamura was already working on projects involvinggallium phosphorus for the company when Akasaki’s group announced their method of creating highquality gallium nitride.
And Nakamura took note.
He asked for permission to pursue the creationeven better quality gallium nitride for Nichia, at a cost of five hundred million yen; which was abouttwo percent of the entire company's sales that year.
It was a massive amount indeed, but they grantedhim permission and the work began.
The first breakthrough came by using thermalannealing instead of an electron beam, which resulted in a higher quality LED but alsoappeared more violet than it did blue.
Another thing he did was create a double heterostructure, basically a sandwich of iridium-infused gallium nitride and the existing GaN crystals, whichnarrowed the bandwidth of the light to appear blue and was tweaked to help create a brighterLED.
Finally on November 29, 1993, Nichia Corporationand Nakamura made public their version of the blue LED, one that was a hundred timesbrighter and more vivid than those of the past.
And it was affordable to create! So Nichia put it into production immediately, and Nakamura continued to work on the project, doubling the brightness of their blue LED inMay of 1994.
Logically following blue were high-intensitywhite LEDs in 1995, produced by adding a yellow phosphor to the blue diode, converting itssky blue light to a vivid white.
Other companies began to follow suit and started producingtheir own versions of blue LEDs, and what resulted was an explosion of LED usage.
Now we finallyhad the full color spectrum through LEDs, and they’re used in everything from homeappliances, to televisions screens and backlighting, to cell phone and tablet displays.
And the altered blue LEDs that result in whitelight have created a revolution of sorts in general lighting applications by being far more energyefficient and longer-lasting alternatives to incandescent and fluorescent bulbs.
Not to mention home lightning is more versatileand colorful than ever, with RGB LEDs combining to create vivid displays in everything frommood lighting bulbs to gaming keyboards.
Another advancement birthed from the blueLED arrived in 1996, where Nakamura built on his work to produce the first efficientblue laser.
While it took some time for the effects of blue LEDs to really be noticed, the benefit of a blue laser was immediatecause for excitement within the data storage community.
Up to that point, lasers for media storagewere only available in red, and their lower wavelength meant you could only store so muchdata on things like CDs and DVDs.
But with blue lasers, or more accurately blue-violetin this case, the potential for higher capacity optical media was huge.
Blu-ray discs are perhaps the most well-known applicationfor blue-violet lasers, but they’re also used in plenty of video projectors, telecommunicationsdevices, and medical diagnostic equipment.
But while there’s always more to talk about on a subject like this, that’s all for this video regarding the blue LED and the struggle to bring it to life.
Without them, we wouldn’t have nearly thesame devices and technology in the 21st century that we do.
From smartphones to street lamps, from toastersto headlights.
There are few pieces of tech today that haven’tbeen affected by the blue LED in some way, so it’s little wonder that Akasaki, Amano, and Nakamura were awarded the Nobel Prize in Physics 2014 for their creations.
At the same time, it’s important to rememberthe decades-long mission to invent the blue LED, spread across countless researchers, companies, and events over the course of the 20th century.
Technological breakthroughs rarely happenin a bubble, and the creation of blue LEDs is very much a worldwide story of successthat only happened through years of failure, persistence, iteration, collaboration, and hardcore science.
And if enjoyed this episode of Tech Tales and my very genuine attempts to pronounce names and scientific terms that I don't say out loud every day, then perhaps you'd like to watch some of my others.
And there are other videos going up every Monday and Friday here on LGR.
And as always, thank you very much for watching!.