Kind: captions
Language: en
LEDs don't get their color from their
plastic covers and you can see that
because here is a transparent LED that
also glows the same red color the color
of the light comes from the electronics
themselves the casing just helps us tell
different LEDs apart in 1962 general
electric engineer Nick holac created the
first visible LED it glowed a faint red
a few years after that engineers at
Monsanto created a green LED but for
decades all we had were those two colors
so LEDs could only be used in things
like indicators calculators and watches
if only we could make blue then we could
mix red green and blue to make white and
every other color unlocking LEDs for
every type of lighting in the world from
light bulbs to phones to computers to
TVs to
Billboards but blue was almost
impossible to
make throughout the 1960s every big
electronics company in the world from
IBM to GE to Bell Labs raced to create
the blue LED they knew it would be worth
billions despite the efforts of
thousands of researchers nothing worked
10 years after hak's original LED turned
into 20 then 30 and the hope of ever
using LEDs for light faded away
according to a director at Monsanto
these won't ever replace the kitchen
light they'd only be used in appliances
car dashboards and stereo sets to see if
the stereo was
on this might still be true today if not
for one engineer who defied the entire
industry and made three radical
breakthroughs to create the world's
first blue
LED shuji Nakamura was a researcher at a
small Japanese chemical company named
Nish they had recently expanded into the
production of semiconductors to be used
in the manufacturer of red and green
LEDs but by the late 1980s the
semiconductor division was on its last
legs they were competing against far
more established companies in a crowded
market and they were losing tensions
started to run High younger employees
begged Nakamura to create new products
while senior workers called his research
a waste of money and at nishia money was
in short
supply nakamura's last mainly consisted
of Machinery he had scavenged and welded
together himself phosphorus leaks in his
lab created so many explosions that his
co-workers had stopped checking in on
him by 1988 nakamura's supervisors were
so disillusioned with his research that
they told him to quit so it was out of
desperation that he brought a radical
proposal to the company's founder and
president nobuo
oawa The elusive blue LED that the likes
of Sony to Sheba and Panasonic had all
failed at what if nishia could be the
one to create it after suffering loss
after loss on their semiconductors for
more than a decade agawa took a gamble
he devoted 500 million yen or $3 million
likely around 15% of the company's
annual profit to nakamura's moonshot
project everyone knew that LEDs had the
potential to replace light bulbs because
light bulbs the universal symbol for a
bright idea are actually terrible at
making light they work by running
current through a Tungsten filament
which gets so hot it glows but most of
the electromagnetic radiation comes out
as infrared heat only a negligible
fraction is visible light in contrast
LED stands for light emitting diode it's
right there in the name LEDs primarily
create light so they're far more
efficient and a diode is just a device
with two electrodes which only allows
current to flow in One
Direction so here's how an LED works
when you have an isolated atom each
electron in that atom occupies a
discrete energy level you can think of
these energy levels like individual
seats from a hockey stadium and all
atoms of the same element when they are
far apart from each other have identical
available energy levels but when you
bring multiple atoms together to form a
solid something interesting happens the
outermost electrons now feel the pull
not only of their own nucleus but of all
the other nuclei as well and as a result
their energy levels shift so instead of
being identical they become a series of
closely spaced but separate energy
levels an energy band the highest energy
band with electrons in it is known as
the veence band and the next higher
energy band is called the conduction
band you can think of it like the
balcony level in conductors the veence
band is only partially filled this means
with a little bit of thermal energy
electrons can jump into nearby unfilled
seats and if an electric field is
applied they can jump from one unfilled
seat to the next and conduct current
through the
material in insulators the veence band
is full and the difference in energy
between the veence and conduction bands
the band Gap is large so when an
electric field is applied no electrons
can move there are no available seats to
move into in the veence band and the
band Gap is too big for any electrons to
jump into the conduction band which
brings us to
semiconductors semiconductors are
similar to insulators except the band
Gap is much smaller this means at room
temperature a few electrons will have
sufficient energy to jump into the
conduction band and now they can easily
access nearby empty seats and conduct
current not only that the empty seats
that they left behind in the veence band
can also move well really it's the
nearby electrons jumping into those
empty seats but if you look from afar
it's as though the empty seat or hole is
moving like a positive charge in the
opposite direction to the electrons in
the conduction
Band by themselves pure semiconductors
are not that useful to make them way
more functional you have to add impurity
atoms into the lattice this is known as
doping for example example in Silicon
you can add a small number of phosphorus
atoms phosphorus is similar to Silicon
so it easily fits into the lattice but
it brings with it one extra veence
electron this electron exists in a donor
level just beneath the conduction band
so with a bit of thermal energy all
these electrons can jump into the
conduction band and conduct current
since most of the charges that can move
in this type of semiconductor are
electrons which are negative this sort
of semiconductor is called n Type n for
negative
but I should point out that the
semiconductor itself is still neutral
it's just that most of the mobile charge
carriers are negative they are electrons
so there is also another type of
semiconductor where most of the mobile
charge carriers are positive and it's
called ptype
to make ptype silicon you add a small
number of atoms of say Boron Boron fits
into the lattice but brings with it one
fewer valence electron than silicon so
it creates an empty acceptor level just
above the veence band and with a bit of
thermal energy electrons can jump out of
the veence band leaving behind holes it
is these positive holes which are mostly
responsible for carrying current in the
ptype semiconductor again the material
overall is uncharged it's just that most
of the mobile charge carriers are
positive holes where things get
interesting is when you put a piece of
ptype and N type together without even
connecting this to a circuit some
electrons will diffuse from n to p and
fall into the holes in the ptype this
makes the ptype a little negatively
charged and the N type a little
positively charged so there is now an
electric field inside an inert piece of
material electrons keep diffusing until
the electric field becomes so large it
prevents them from crossing over and now
we have established the depletion region
an area depleted of mobile charge
carriers there are no electrons in the
conduction band and no holes in the
veence band if you connect a battery the
wrong way to this diode it simply
expands the depletion region until its
electric field perfectly opposes that of
the battery and no current
flows but if you flip the polarity of
the battery then the depletion region
shrinks the electric field decreases and
electrons can flow from n to P when an
electron falls from the conduction band
into a hole in the veence band that band
Gap energy can be emitted as a photon
the energy change of the electron is
emitted as light and this is how a light
emitting diode works the size of the
band Gap determines the color of the
light emitted in pure silicon the band
Gap is only 1.1 electron volts so the
photon released isn't visible it's
infrared light these LEDs are actually
used in remote controls like for your TV
and you can capture them on camera
moving up the Spectrum you can see why
the first visible light LEDs were red
and then green and why blue was so hard
a photon of blue light requires more
energy and therefore a larger band
Gap by the 1980s after hundreds of
millions of dollars had been spent
hunting for the right material every
electronics company had come up
empty-handed but researchers had at
least figured out the first critical
requirement highquality Crystal no
matter what material you used for the
blue LED it required a near-perfect
crystal structure any defects in the
crystal lce disrupt the flow of
electrons so instead of emitting their
energy as visible light it is instead
dissipated as heat so the first step in
nakamura's proposal to agawa was to
disappear to Florida he knew an old
colleague there whose lab was beginning
to use a new Crystal making technology
called metal organic chemical vapor
deposition or
mocvd an mocvd reactor essentially a
giant oven was and still is the best way
to mass-produce clean Crystal it works
by injecting Vapor molecules of your
Crystal into a hot chamber where they
react with a base material called a
substrate to form layers it's important
that the substrate lattice matches the
crystal latus being built on top of it
to create a stable smooth Crystal this
is a precise art the crystal layers
often need to be as thin as just a
couple of atoms Nakamura joined the lab
for a year to m
MBD but his time there was
miserable he wasn't allowed to use the
working mocvd so he spent 10 of his 12
months assembling a new system almost
from scratch even worse his labmates
shunned him because Nakamura didn't have
a doctorate nor any academic papers to
his name as nishia didn't allow
publishing his labmates all PhD
researchers dismissed him as a lowly
technician this experience fueled him
Nakamura wrote I feel resentful when
people look down on me I developed more
fighting spirit I would not allow myself
to be beaten by such
people he returned to Japan in 1989 with
two things in hand one an order for a
brand new MBD reactor for Nish and two a
fervent desire to get his PhD at that
time in Japan you could earn a PhD
without having to go to university
simply by publishing five
papers Nakamura had always known his
chances of inventing the blue LED were
low but now he had a backup plan even if
he didn't succeed he could at least get
his PhD but now the question was with
mocvd under his belt which material
should he
research by this time scientists had
narrowed the options down to two main
candidates zinc selenide and gallium
nitride these were both semic conductors
with band gaps theoretically in the blue
light range zinc selenide was the far
more promising option when grown in an
mocvd reactor it had only a 3% lattice
mismatch with its substrate gallium
arsenide therefore zinc selenide Crystal
had about 1,000 defects per square cm
within the upper limit for Led
functioning its only issue was that
while scientists had figured out
multiple different ways to create n type
zinc selenide no one knew how to create
ptype
Ty in contrast gallium nitride had been
abandoned by almost everybody for three
reasons first it was much harder to make
a highquality crystal the best substrate
for growing gallium nitride was Sapphire
but its lattice mismatch was
16% this resulted in higher defects over
10 billion per square cm the second
problem was that like zinc selenide
scientists had only ever created nype
Gallum nitride using
P type was
Elusive and third to be commercially
viable a blue LED would have to have a
total light output power of at least
1,000 microwatt that's two orders of
magnitude more than any prototype had
ever
achieved so between the two candidates
almost all researchers were focused on
zinc
selenide Nakamura surveyed the crowded
field and decided that if he were going
to publish five papers by himself he'd
better focus on on gallium nitride where
the competition was much less Fierce
this material's main claim to fame was
one development back in 1972 when RCA
engineer Herbert marusa made a tiny
gallium nitride blue LED but it was dim
and inefficient so RCA slashed the
Project's budget calling it a dead end
20 years later scientific opinion hadn't
changed when Nakamura attended the
biggest Applied Physics conference in
Japan the talks on zinc selenide had
over 500 attendees the toxon Gallum
nitride had
five two of those five attendees were
the world experts on gallium nitride Dr
isamu akazaki and his former grad
student Dr Hoshi Amano in contrast to
nakamura's academic background they were
researchers at ngoya University one of
Japan's best a few years earlier they
had made a breakthrough on the first
problem of highquality Crystal instead
of growing G nitride directly on
Sapphire they first grew a buffer layer
of aluminum nitride this has a Lattis
spacing in between that of the other two
materials making it easier to grow a
clean gallium nitride Crystal on top the
only issue was that the aluminum caused
problems for the mocvd reactor making
the process hard to scale but Nakamura
wasn't even close at this
stage back at nishia he couldn't get
gallium nitride to even grow normally in
his new MBD reactor after 6 months
desperate for results he decided to take
the machine apart and build a better
version
himself his 10 months spent putting
together the reactor in Florida were
suddenly invaluable he began following
the same routine each day arrive at the
lab at 7:00 a.m. spend the first half of
the day welding cutting and rewiring the
reactor spend the rest of the day
experimenting with the modified reactor
to see what it can do at 7:00 p.m. go
home eat dinner wash and sleep Nakamura
repeated this routine every single day
taking no weekends and no holidays
except for New Year's Day the most
important holiday in
Japan after a year and a half of
continuous work he came into the lab on
a winter day in late
1990 as usual he tinkered around in the
morning grew a gallium nitride sample in
the afternoon and tested
it but this time the electron Mobility
was four times higher than any gallium
nitride ever grown directly on Sapphire
Nakamura called it the most exciting day
of his
life his trick was to add a second
nozzle to the mocvd reactor the gallium
nitride reactant gases had been rising
in the hot chamber mixing in the air to
form a powdery waste but the second
nozzle released a downward stream of
inert gas pinning the first flow to the
substrate to form a uniform Crystal for
years scientists had avoided adding a
second stream to mocvd because they
thought it would only introduce more
turbulence but Nakamura used a special
nozzle so that even when the streams
combined they remained laminer he called
his invention the two-flow
reactor now he was ready to take on
akazaki and Amano but instead of copying
their aluminum nitride buffer layer his
two-flow design allowed him to make
gallium nitride so smooth and stable it
itself could be used as a buffer layer
on the sapphire substrate this in turn
yielded an even cleaner Crystal of
gallium nitrite on top without the
issues of aluminum Nakamura now had the
highest quality gallium nitride crystals
ever made but just as he was getting
started things took a wrong
turn while he had been in Florida
Florida NOA Ogawa had stepped back from
nishia to become chairman in his day NOA
had been a risk-taking scientist
designing the company's first products
it's why he supported nakamura's lofty
plans all this time but in his place his
son-in-law AJ Ogawa became CEO of the
company and the younger Ogawa had a much
stricter Outlook one nishia client said
he has a mind of Steel and he remembers
everything in 1990 an executive at
matsua an LED manufacturer and nish's
biggest customer visited the company to
give a talk on Blue LEDs in it he
claimed zinc selenide was the way
forward declaring gallium nitride has no
future that very same day Nakamura
received a note from AG stop work on
gallium nitride
immediately AG had never supported the
research and wanted to end what he saw
as a colossal waste but Nakamura
crumpled up the note and threw it away
and he did so again and again when a
succession of similar notes and phone
calls came from company management out
of spite he published his work on the
two-flow reactor without nisha's
knowledge it was his first paper one
down four to
go with Crystal formation settled he
turned to the second obstacle creating
ptype gallium nitride here akazaki and
amount had again beaten him to the punch
they had created a gallium nitrite
sample doped with magnesium but at first
it didn't perform as a ptype as they
expected however after exposing it to an
electron beam it did behave as a ptype
the world's first ptype gallium nitrite
after 20 years of trying the catch was
that no one knew why it worked and the
process of radiating each Crystal with
electrons was too slow for commercial
production
at first Nakamura copied akazaki and
amano's approach but he suspected the
beam of electrons was Overkill maybe all
the crystal needed was energy so he
tried heating magnesium doped Gallum
nitride to 400° C in a process known as
analing the result a completely ptype
sample this worked even better than the
shallow Electron Beam which only made
the surfaces of the samples ptype and
simply heating things up was a quick
scalable process his work also revealed
why the ptype had been so difficult to
make gallium nitride with mocvd you
supply the nitrogen from ammonia but
ammonia also contains hydrogen where
there should have been holes in the
Magnesium doped gallium nitride these
hydrogen atoms were sneaking in and
bonding with the Magnesium plugging all
the holes adding energy to the system
released the hydrogen from the material
freeing up the holes again
by now Nakamura had all the ingredients
to make a prototype blue LED and he
presented it at a workshop in St Louis
in 1992 and received a standing ovation
he was beginning to make a name for
himself but even though he had created
the best prototype to date it was more
of a blue violet color and still
extremely inefficient with a light
output power of just 42 microwatt well
below the 1,000 microwatt Thresh hold
for practical
use at nishia the new CEO's patients had
run out AG sent written orders to
Nakamura to stop tinkering and turn
whatever he had into a product his job
was on the line but in nakamura's own
words I kept ignoring his order I had
been successful because I didn't listen
to company orders and trusted my own
judgment at this point he only had the
third hurdle left getting his blue LED
to a light output power of a000 th000
microwatts a known trick to increase the
efficiency of LEDs was to create a well
a thin layer of material at the PN
Junction called an active layer that
shrinks the band Gap just a bit this
encourages more electrons to fall from
the N type conduction band into holes in
the ptype veence band the best active
layer for gallium nitride was already
known to be indium gallium nitride which
would not only make the band Gap easier
to cross but also narrow it just the
right amount to bring its blue violet
gap down to True Blue this time akazaki
and Amano didn't scoop Nakamura they
were stuck trying to grow indium gallium
nitride in the first place Amano recall
it was generally said that gallium
nitride and indium nitride would not mix
like water and oil but Nakamura had an
advantage his ability to customize his
mocvd reactor this allowed him to use
brute force
adjusting the reactor to pump as much
indium as he could onto the gallium
nitride in the hopes that at least some
would stick to his surprise the
technique worked giving him a clean
indium gallium nitride Crystal he
quickly Incorporated this active layer
into his LED but the well worked a
little too well and overflowed with
electrons leaking them back into the
Gallum nitride layers unfazed within a
few months Nakamura had fixed this too
by creating the opposite of a well a
hill he returned to his reactor one more
time to make aluminum gallium nitride a
compound with a larger band Gap that
could block electrons from escaping the
well once
inside the structure of the blue LED had
become far more complex than anyone
could have
imagined but it was complete by 1992
shuji Nakamura had
this and I show the chairman I told
please come to my you know office I show
and said oh this great know I became so
happy
I yeah after 30 years of searching by
countless scientists Nakamura had done
it he had created a glorious bright blue
LED that could even be seen in daylight
it had a light output power of 1,500
microwatt and emitted a perfect blue at
exactly 450 nanom it was over 100 times
brighter than the previous pseudo blue
LEDs on the market Nakamura wrote I felt
like I had reached the top of Mount Fuji
nishia called a press conference in
Tokyo to announce the world's first true
blue LED the electronics Industry was
stunned a researcher from tashiba
remarked everyone was caught with their
pants down the effect on nish's fortunes
was immediate and explosive orders
flooded in and by the end of 1994 they
were manufacturing 1 million blue LEDs
per month within 3 years the company's
Revenue had nearly doubled in 1996 they
made the jump from Blue to White by
placing a yellow phosphor over the LED
this chemical absorbs the blue photons
and radiates them in a broad spectrum
across Ross the visible range soon
enough Nisha was selling the world's
first white LED at last unlocking the
final frontier so many had doubted LED
lighting over the next 4 years their
sales doubled Again by 2001 their
revenue was approaching $700 million a
year over 60% came from blue LED
products today nishia is one of the
largest LED manufacturers in the world
with an annual revenue in the
billions as for Nakamura to whom nishia
owed the quadrupling of its
fortunes I increased my salary
60,000 yeah I heard you only got a $170
bonus it's patent patent patent so you
got $170 bonus for the patent yes yes
this was all while the blue LED was
generating hundreds of millions of
dollars in sales
AG oawa had always seen nakamura's
stubborn individuality as a liability
not a strength the message was clear in
2000 after more than 20 years at nishia
Nakamura left the company for the US
where job offers had been pouring in but
his troubles with nishia weren't over he
began Consulting for cre another LED
company nishia was Furious and sued him
for leaking company Secrets Nakamura
responded by countersuing nishia for
never properly compensating him for his
invention seeking $20
million in 2001 the Japanese courts
ruled with Nakamura and ordered Nish to
pay him 10 times his initial request but
Nish appealed and the case was
eventually settled with a payout of $8
million in the end this was only enough
to cover nakamura's legal
fees this is all he got for an invention
that now comprises an $80 billion
industry from house lights to street
lights while you watch this video on a
phone computer or TV if you're outside
following traffic lights or displays
chances are you are relying on Blue
[Music]
LEDs we might even be getting too much
of them you may have heard warnings to
avoid blue light from screens before bed
because it can disrupt your circadian
rhythm that all comes from the gallium
nitride blue
LED but as for lighting there are
virtually no downsides to an LED bulb
compared to an incandescent or
fluorescent bulb they are far more
efficient they last many times longer
are safer to handle and are completely
customizable 30 years after the first
white LED high-end bulbs today allow you
to choose between 50,000 different
shades of white
most importantly their price has come
down to only a couple of dollars more
than other types of bulbs and at their
efficiency with average daily use and
electricity pricing you can recoup that
cost in only two months and continue to
save for years after that the result is
a lighting revolution in 2010 just 1% of
residential lighting sales in the world
were LED in 2022 it was over half
experts estimate that within the next
next 10 years nearly all lighting sales
will be
led the Energy savings will be enormous
lighting accounts for 5% of all carbon
emissions a full switch to LEDs could
save an estimated 1.4 billion tons of
CO2 equivalent to taking almost half the
cars in the world off the
road today nakamura's research is on the
next generation of LEDs micro LEDs and
UV LEDs
so what are they making in there uh LED
is a power device this is one of the
best
POS and this is because of
you well what's a standard LED size 300
* 200 microns smallest is 5
microns that is insanely tiny Yeah so
basically you can use that like near ey
displays such as AR and VR you could
have like a retina display that's like
like right up here yep human hair would
be about that thick yep and that's a
really really tiny
LED UV LEDs could be used to sterilize
surfaces like in hospitals or kitchens
just flick on the UV lights and
pathogens would be dead in seconds
covid-19 you know you know U company
stop kind of because everybody expect
using this U ads we can all the 19
forting we use
Indian for U we use aluminum nitrate
okay because B Gap is much bigger do you
think this is what's coming it's okay it
work but probably the cost cost is too
high CH is less than 10% the cost is
very high but if the efficiency become
more than 50 CL is almost comparable the
market and you think it will happen
right like the efficiency will go up
yeah yeah I think so it's just a matter
of time yes I think so and he's even
tackling one of the biggest challenges
of our time I interested in physics so
me too I'm still interested nuclear fion
so recently I started the company of
nuclear fion really oh yeah yeah no way
no
way in 2014 Nakamura akazaki and Amano
were awarded the Nobel Prize in physics
for creating the blue LED shortly
afterwards Nakamura publicly thanked
nishia for supporting his work and he
offered to visit and make amends but
they turned down his offer and today
their relationship is still cold but
perhaps even more important than the
Nobel Prize by the time Nakamura
released his blue LED in 1994 he had
published over 15 papers and he finally
received his Doctorate in engineering
today he has published over 900 papers
throughout his entire Journey one thing
has never changed what is your favorite
color oh we don't know
was it always blue or only after you
made the LED I was born the fish C fish
in front the house is like
ocean well I was learning about
nakamura's story I realized that what
set him apart from the thousands of
researchers trying to unlock the blue
LED it wasn't necessarily his knowledge
but his determination critical thinking
and problem solving skills where others
saw dead ends he saw potential Solutions
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