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 Holonyak

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.

(dramatic music)

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 Holonyak'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.

(dramatic music)

Shūji Nakamura was a researcher at a small Japanese chemical

company named Nichia.

They had recently expanded into the production

of semiconductors to be used in the manufacture

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 Nichia, money was in short supply.

Nakamura's lab mainly consisted of machinery

he had scavenged and welded together himself.

Phosphorus leaks in his lab created so many explosions,

that his coworkers 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 Ogawa.

(dramatic music)

The elusive blue LED,

that the likes of of Sony, Toshiba and Panasonic

had all failed at.

What if Nichia could be the one to create it?

After suffering loss after loss on their semiconductors

for more than a decade,

Ogawa 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 have 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 discreet 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 pole,

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 valence band,

and the next higher energy band

is called the conduction band.

You can think of it like the balcony level.

In conductors, the valence 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 valence band is full,

and the difference in energy between the valence

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 valence 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 they left

behind in the valence 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.

(soft music)

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, 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 valence 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're electrons.

So there is also another type of semiconductor where most

of the mobile charge carriers are positive,

and it's called p-type.

To make p-type 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 valence band.

And with a bit of thermal energy,

electrons can jump outta the valence band,

leaving behind holes.

It is these positive holes which are mostly responsible

for carrying current in the p-type 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 p-type 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 p-type.

This makes the p-type 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 valence 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 valence 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

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, high quality crystal.

No matter what material you used for the blue LED,

it required a near perfect crystal structure.

Any defects in the crystal lattice,

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 Ogawa,

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 lattice 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 master MOCVD.

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,