Invention of the First Transistor,
November 17-December 23, 1947
On November 17, 1947, Walter Brattain dumped his whole
experiment into a thermos of water. The silicon contraption he'd built
was supposed to help him study how electrons acted on the surface
of a semiconductor -- and why whatever they were doing made it impossible
to build an amplifier. But condensation kept forming on the silicon
and messing up the experiment. To get rid of that condensation, Brattain
probably should have put the silicon in a vacuum, but he decided that
would take too long. Instead he just dumped the whole experiment under
water -- it certainly got rid of the condensation!
Out of the blue, the wet device created the largest
amplification he'd seen so far. He and another scientist, Robert Gibney,
stared at the experiment, stunned. They began fiddling with different
knobs and buttons: by turning on a positive voltage they increased
the effect even more; turning it to negative could get rid of it completely.
It seemed that whatever those electrons had been doing on the surface
to block amplification had somehow been canceled out by the water -- the
greatest obstacle to building an amplifier had been overcome.
the Idea to Use
When John Bardeen was told what had happened he thought
of a new way to make an amplifier. On November 21, Bardeen suggested
pushing a metal point into the silicon surrounded by distilled water.
The water would eliminate that exasperating electron problem just
under the point as it had in the thermos. The tough part was that
the contact point couldn't touch the water, it must only touch the
silicon. But as always, Brattain was a genius in the lab. He could
build anything. And when this amplifier was built, it worked. Of course,
there was only a tiny bit of amplification -- but it worked.
Once they'd gotten slight amplification with that tiny
drop of water, Bardeen and Brattain figured they were on the road
to something worthwhile. Using different materials and different setups
and different electrolytes in place of the water, the two men tried
to get an even bigger increase in current. Then on December 8, Bardeen
suggested they replace the silicon with germanium. They got a current
jump, all right -- an amplification of some 330 times -- but in the
exact opposite direction they'd expected. Instead of moving the electrons
along, the electrolyte was getting the holes moving. But amplification
is amplification -- it was a start.
Makes a Mistake
Unfortunately this giant jump in amplification only
worked for certain types of current -- ones with very low frequencies.
That wouldn't work for a phone line, which has to handle all the complex
frequencies of a person's voice. So the next step was to get it to
work at all kinds of frequencies.
Bardeen and Brattain thought it might be the liquid
which was the problem. So they replaced it with germanium dioxide -- which
is essentially a little bit of germanium rust. Gibney prepared a special
slab of germanium with a shimmering green oxide layer on one side.
On December 12, Brattain began to insert the point contacts.
In fact the device worked as if there was no oxide layer
at all. And as Brattain poked the gold contact in again and again,
he realized that's because there wasn't an oxide layer. He had washed
it off by accident. Brattain was furious with himself, but decided
to fiddle with the point contact anyway. To his surprise, he actually
got some voltage amplification -- and more importantly he could get
it at all frequencies! The gold contact was putting holes into the
germanium and these holes canceled out the effect of the electrons
at the surface, the same way the water had. But this was much better
than the version that used water, because now, the device was increasing
the current at all frequencies.
it All Together
In the past month, Bardeen and Brattain had managed
to get a large amplification at some frequencies and they'd gotten
a small amplification for all frequencies -- now they just had to combine
the two. They knew that the key components were a slab of germanium
and two gold point contacts just fractions of a millimeter apart.
Walter Brattain put a ribbon of gold foil around a plastic triangle,
and sliced it through at one of the points. By putting the point of
the triangle gently down on the germanium, they saw a fantastic effect
-- signal came in through one gold contact and increased as as it raced
out the other. The
first point-contact transistor had been made.
For a week, the scientists kept their success a secret.
Shockley asked Bardeen and Brattain to show off their little plastic
triangle at a group meeting to the lab and the higher-ups on December
23. After the rest of the lab had a chance to look it over and conduct
a few tests, it was official -- this tiny bit of germanium, plastic
and gold was the first working solid state amplifier.
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