The blue LED.
You may consider it a pretty mundane aspect of modern life, largely relegated to simple
tasks such as indicating power and illuminating holiday lights.
Ubiquitous as they are now though, they’re a relatively recent invention, and until 1993
there was no such thing as a commercially viable blue LED.
Yet without them so much of our modern tech would 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 look at noteworthy stories of technological inspiration,
failure, and everything in-between.
This episode tells the tale of the decades-long struggle to create the blue LED.
Our story begins in 1907 with the emergence of the light-emitting diode.
Henry Joseph Round discovered that if you touch two metal needles to a crystal of silicon
carbide and apply electricity, you’d sometimes see a very dim light glowing color.
Silicon carbide, while often used in things like sandpaper, is actually a semiconducting
material, and the electrified needles created a 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 for a practical LED to be produced.
An important step in this direction came from Dr. Rubin Braunstein at RCA in 1955 that showed an infrared emission
from semiconductor alloys like gallium arsenide.
This was followed up in 1961 at Texas Instruments by James Biard and Gary Pittman, who discovered
a 900nm near-infrared light emission on a gallium substrate.
The same method would also be used
at General Electric to create a more visible LED through 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 compositions were 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 of the brightest and most cost-effective to manufacture,
initially sold to the military and companies like Hewlett Packard, before appearing in
consumer products like the pocket calculators of the early 1970s.
Soon, LEDs were popping up in electronics all over the place, finding uses in everything
from computer displays, to telephone keypad lighting.
However, there was still a primary color that remained elusive.
Blue.
The idea of a blue LED was highly desirable since 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 completely to create white.
And the reason LEDs were stuck with various hues of red, yellow, and green, but not blue,
is down to the physics in how light is produced on a diode to begin with.
To put it very simply, an LED is made up of multiple layers of positive and negative semiconductor materials,
and when electricity passes through them, they emit light 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 light is much higher than red, yellow, and even green,
it required far more exotic materials and production processes to reproduce.
Some of the early blue LEDs were developed at RCA in 1972, while attempting to come up
with a television that used LEDs instead of phosphors in cathode ray tubes.
That breakthrough was achieved at RCA that year by Herbert Maruska, accomplished by first
figuring out how to grow crystals of gallium nitride, and then “doping” them with magnesium.
But unfortunately the resulting light was too dim to be practical,
and seeing as RCA was in financial trouble going into the mid-70s, further development
was halted.
So, gallium nitride and magnesium.
The groundwork was there, but there were huge obstacles to overcome to make this light bright
enough to be useful and cheap enough to be practical.
Companies like Bell Labs and Matsushita continued working with these materials for years, before
coming to the conclusion that gallium nitride was unlikely to result in viable blue LEDs
since it was so tough to work with.
Growing the crystals in high enough quality and quantity was stupidly challenging, and
reliably producing the exact types of positive and negative layers required was even harder.
It was not until the 1980s that these obstacles would be overcome, and it was largely thanks
to a string of breakthroughs by three men in Japan.
The first is Isamu Akasaki, who was a physicist at Nagoya University leading a group in coming
up with a better method of growing gallium nitride.
Next is Hiroshi Amano, an undergraduate researching the growth of nitride semiconductors, who
joined Akasaki’s group in 1982.
And finally we have Shuji Nakamura, an electronic engineer specializing in semiconductor tech
at the Nichia Corporation in Tokushima.
It was in 1985 that Amano first had promising results in making high quality gallium nitride
by using what the team called ‘low-temperature buffer layer technology.’
This was an important step to growing high quality crystals, but it didn’t solve
the problem of producing an efficient positive and negative junction.
That didn’t happen until 1989, when Akasaki’s group finally succeeded in fabricating the
correct layers by irradiating the crystals with a high-powered electron beam.
The results still were too complicated and costly to be used commercially, but the results
and the research were made available for people to read.
People like Shuji Nakamura, who was working on creating new products for the Nichia Corporation.
At the time, Nichia was known for producing phosphors used in fluorescent lights and color
cathode ray tubes, but were looking for a fresh new product with fewer competitors.
Nakamura was already working on projects involving gallium phosphorus for the company when Akasaki’s
group announced their method of creating high quality gallium nitride.
And Nakamura took note.
He asked for permission to pursue the creation even better quality gallium nitride for Nichia,
at a cost of five hundred million yen; which was about two percent of the entire
company's sales that year.
It was a massive amount indeed, but they granted him permission and the work began.
The first breakthrough came by using thermal annealing instead of an electron beam, which
resulted in a higher quality LED but also appeared 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, which narrowed the bandwidth of the light to appear
blue and was tweaked to help create a brighter LED.
Finally on November 29, 1993, Nichia Corporation and Nakamura made public their version of
the blue LED, one that was a hundred times brighter
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 in May of 1994.
Logically following blue were high-intensity white LEDs in 1995, produced by adding a yellow
phosphor to the blue diode, converting its sky blue light to a vivid white.
Other companies began to follow suit and started producing their own versions of blue LEDs,
and what resulted was an explosion of LED usage.
Now we finally had the full color spectrum through LEDs,
and they’re used in everything from home appliances, to televisions screens and backlighting,
to cell phone and tablet displays.
And the altered blue LEDs that result in white light have created a revolution of sorts in general
lighting applications by being far more energy efficient and longer-lasting alternatives
to incandescent and fluorescent bulbs.
Not to mention home lightning is more versatile and colorful than ever, with RGB LEDs combining
to create vivid displays in everything from mood lighting bulbs to gaming keyboards.
Another advancement birthed from the blue LED arrived in 1996, where Nakamura built
on his work to produce the first efficient blue laser.
While it took some time for the effects of blue LEDs to really be noticed,
the benefit of a blue laser was immediate cause for excitement within
the data storage community.
Up to that point, lasers for media storage were only available in red, and their lower
wavelength meant you could only store so much data on things like CDs and DVDs.
But with blue lasers, or more accurately blue-violet in this case, the potential for higher capacity
optical media was huge.
Blu-ray discs are perhaps the most well-known application for blue-violet lasers, but they’re also
used in plenty of video projectors, telecommunications devices, 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 the same devices and technology in the 21st century that we do.
From smartphones to street lamps, from toasters to headlights.
There are few pieces of tech today that haven’t been 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 remember the 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 happen in a bubble, and the creation of blue LEDs
is very much a worldwide story of success that 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!